Rubber composition and tire

Abstract

To provide a rubber composition that reduces environmental impact while enabling high air permeation resistance and exhibiting good vulcanization properties.SOLUTION: A rubber composition contains a rubber component including a butyl-based rubber and cellulose nanofibers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rubber composition and a tire. [Background technology]

[0002] Most tires are equipped with an inner liner to maintain air pressure inside the tire and maintain driving characteristics and durability. This inner liner is usually made of a rubber material with low air permeability (high air permeability resistance), and the inner liner is produced by vulcanizing such a rubber material.

[0003] When the air pressure inside a tire decreases, the tire deforms significantly and rolling resistance worsens. This deterioration in rolling resistance is directly linked to carbon dioxide emissions and is also related to environmental issues. For this reason, maintaining air pressure inside a tire by using an inner liner is also important from the perspective of environmental impact.

[0004] Many conventional inner liners reduce air permeability by blending clay. Air has the property of detouring around foreign objects, a phenomenon known as the maze effect. Clay has a strong maze effect, and the use of clay with a particularly high degree of flatness can effectively increase air permeability resistance.

[0005] Clay is a mineral resource extracted from mines, and in recent years there has been a demand for the development of alternative materials that can exhibit air permeability resistance equal to or greater than that of clay used as a filler.

[0006] To meet the above demands, for example, Patent Document 1 discloses that oxygen permeability can be reduced by blending lignin in addition to blending a filler such as clay.

[0007] Furthermore, Patent Document 2 discloses that gas permeability can be reduced by blending lignin alone as a filler. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2023-522255 [Patent Document 2] Special Publication No. 2023-541734 Summary of the Invention [Problem to be solved by the invention]

[0009] However, it has been found that when lignin is blended with a rubber material and then vulcanized, the vulcanization characteristics deteriorate, such as an increase in the blow point (the minimum degree of vulcanization required for bubbles to disappear at the end of vulcanization). Such deterioration in vulcanization characteristics also affects the quality of the resulting rubber components, such as inner liners, so it is important to avoid or suppress it.

[0010] Therefore, an object of the present invention is to provide a rubber composition that has a small environmental impact, exhibits high air permeation resistance, and has good vulcanization characteristics, and a tire using the same. [Means for solving the problem]

[0011] That is, the gist of the present invention for solving the above problems is as follows.

[0012] [1] A rubber composition comprising a rubber component containing a butyl rubber and cellulose nanofibers.

[0013] [2] The rubber composition according to [1], wherein the cellulose nanofibers have an aspect ratio of 3 or more.

[0014] [3] The rubber composition according to [1] or [2], wherein the cellulose nanofiber has a modifying group.

[0015] [4] The rubber composition according to any one of [1] to [3], wherein the content of the cellulose nanofibers is 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the rubber component.

[0016] [5] The rubber composition according to any one of [1] to [4], further containing carbon black.

[0017] [6] The rubber composition according to any one of [1] to [5], wherein the content of natural rubber is less than twice the content of the cellulose nanofibers.

[0018] [7] The rubber composition according to any one of [1] to [6], wherein the proportion of the isoprene-based rubber in the rubber component is less than 5 mass %.

[0019] [8] The rubber composition according to any one of [1] to [8], which is for use in an inner liner of a tire.

[0020] [9] A tire comprising the rubber composition according to any one of [1] to [8]. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a rubber composition that has a small environmental impact, exhibits high air permeation resistance, and has good vulcanization characteristics, and a tire using the same. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a graph showing vulcanization curves for the rubber compositions of Reference Example 1, Comparative Example 1, and Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described. However, the description is intended to exemplify the present invention and is not intended to limit the present invention in any way.

[0024] The compounds described herein may be derived partially or entirely from fossil resources, biological resources such as plant resources, or recycled resources such as used tires, or may be derived from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0025] <Rubber composition> A rubber composition according to one embodiment of the present invention (hereinafter sometimes referred to as "the rubber composition of this embodiment") is characterized by containing a rubber component including a butyl-based rubber and cellulose nanofibers (hereinafter sometimes abbreviated as "CNF").

[0026] The rubber composition of this embodiment contains butyl rubber and CNF, and the unique interaction between them allows it to exhibit high air permeability resistance. Furthermore, lignin, which has been used as a filler in conventional technology, has a chemical structure containing benzene rings in its molecule, and it is believed that these benzene rings have a negative effect on vulcanization characteristics. On the other hand, CNF has a chemical structure that does not contain benzene rings in its molecule, so it has no or very little negative effect on vulcanization. Therefore, the rubber composition of this embodiment has good vulcanization characteristics. Furthermore, CNF is a so-called biomass material, making it environmentally friendly. Therefore, the rubber composition of this embodiment has a small environmental impact, can exhibit high air permeation resistance, and has good vulcanization characteristics.

[0027] (rubber component) The rubber composition of this embodiment contains at least a butyl-based rubber as a rubber component. Examples of butyl-based rubber include butyl rubber, halogenated butyl rubber, and halogenated isobutylene-p-alkylstyrene copolymer. The butyl-based rubber may be a single type or a combination of two or more types.

[0028] The butyl rubber is typically a rubber obtained by copolymerizing isobutylene with isoprene, and is also called an isobutylene-isoprene copolymer (IIR). The halogenated butyl rubber is a halogenated product of butyl rubber. Examples of the halogenated butyl rubber include chlorinated butyl rubber (ClIIR) and brominated butyl rubber (BrIIR). The halogenated isobutylene-p-alkylstyrene copolymer is a halogenated product of a copolymer of isobutylene and p-alkylstyrene.

[0029] The rubber composition of this embodiment may or may not contain a rubber component other than a butyl-based rubber. Examples of such a rubber component include diene-based rubber components such as isoprene-based rubber (natural rubber (NR) and synthetic isoprene rubber (IR)), styrene-butadiene copolymer rubber (SBR), and butadiene rubber (BR). The rubber component other than the butyl-based rubber may be one type alone or a combination of two or more types.

[0030] In the rubber composition of this embodiment, the proportion of butyl rubber in the rubber component is preferably 50% by mass or more. In this case, air permeation resistance can be more effectively improved. From the same viewpoint, the proportion of butyl rubber in the rubber component is more preferably 70% by mass or more, further preferably 90% by mass or more, and particularly preferably 100% by mass (i.e., the rubber component consists solely of butyl rubber).

[0031] In the rubber composition of this embodiment, the proportion of isoprene-based rubber (natural rubber (NR), synthetic isoprene rubber (IR)) in the rubber component is preferably less than 5% by mass. In this case, air permeation resistance can be more effectively improved. From the same viewpoint, the proportion of isoprene-based rubber in the rubber component is more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass (i.e., the rubber component does not contain isoprene-based rubber).

[0032] In the rubber composition of this embodiment, the content of natural rubber is preferably less than twice the content of CNF. In this case, air permeation resistance can be more effectively improved. From the same viewpoint, it is also preferable that the rubber composition of this embodiment does not contain natural rubber.

[0033] In the rubber composition of this embodiment, the content of synthetic isoprene rubber is preferably less than twice the content of CNF. In this case, air permeation resistance can be more effectively improved. From the same viewpoint, it is also preferable that the rubber composition of this embodiment does not contain synthetic isoprene rubber.

[0034] (Cellulose nanofiber) The rubber composition of this embodiment contains cellulose nanofibers (CNF). Cellulose nanofibers are typically fibers obtained by defibrating a cellulose raw material to the nano-size level. The cellulose nanofibers can be obtained by known methods. For example, the cellulose nanofibers can be obtained by mechanically grinding or beating an aqueous suspension or slurry of the cellulose raw material using a refiner, high-pressure homogenizer, grinder, kneader (extruder), bead mill, or the like.

[0035] In this specification, cellulose nanofibers (CNF) can be handled separately from cellulose nanocrystals (crystals obtained by hydrolyzing and removing the amorphous portion of the cellulose raw material).

[0036] The CNF used in this embodiment preferably has an average diameter of 2 nm or more and 200 nm or less. In this case, the dispersibility of the CNF in the rubber component is improved, and air permeation resistance can be effectively improved. From the same viewpoint, the average diameter of the CNF is more preferably 5 nm or more, even more preferably 10 nm or more, and more preferably 150 nm or less, even more preferably 100 nm or less.

[0037] The CNF used in this embodiment preferably has an average length of 100 nm or more and 300 μm or less. In this case, the dispersibility of the CNF in the rubber component is improved, and air permeation resistance can be effectively improved. From the same viewpoint, the average length of the CNF is more preferably 300 nm or more, and even more preferably 500 nm or more, and more preferably 150 μm or less, and even more preferably 100 μm or less.

[0038] The CNF used in this embodiment preferably has an aspect ratio of 3 or more. In this case, the air permeability resistance can be further improved by the labyrinth effect. From the same viewpoint, the aspect ratio of the CNF is more preferably 10 or more, more preferably 20 or more, more preferably 30 or more, more preferably 50 or more, and even more preferably 75 or more. On the other hand, the upper limit of the aspect ratio of the CNF is not particularly limited, but can be, for example, 150,000 or less, 30,000 or less, or 10,000 or less. The aspect ratio is calculated by dividing the average length by the average diameter.

[0039] The average diameter and length of the CNFs can be measured from an image of the CNFs taken with a microscope such as an atomic force microscope. Alternatively, the average diameter and length of the CNFs can be determined by measuring the diameters and lengths of 10 CNFs and using the average values.

[0040] The CNF used in this embodiment preferably has a modifying group. In this case, the dispersibility of the CNF in the rubber component is improved, and air permeation resistance can be effectively improved. The CNF having a modifying group can be obtained, for example, by modifying the hydroxyl groups in the CNF using a modifying agent. The CNF having a modifying group may be one type alone or a combination of two or more types.

[0041] The modifying group is not particularly limited, and examples thereof include a sulfo group, a carboxymethyl group, a carboxyl group, an aldehyde group, a phosphate group, an epoxy group, and an ester group.

[0042] The sulfo group as a modifying group can be imparted to the CNF by, for example, modifying the CNF using a sulfonating agent such as sulfuric acid, fuming sulfuric acid, chlorosulfuric acid, or fluorosulfuric acid as a modifying agent.

[0043] Carboxymethyl groups as modifying groups can be imparted to CNFs, for example, by modifying the CNFs using a carboxymethylating agent such as monochloroacetic acid, sodium monochloroacetate, methyl monochloroacetate, ethyl monochloroacetate, or isopropyl monochloroacetate as a modifying agent.

[0044] Carboxyl or aldehyde groups as modifying groups can be imparted to CNF by, for example, modifying CNF using an N-oxyl compound as a modifying agent, oxidizing the primary hydroxyl group at carbon 6 of the pyranose ring of cellulose. N-oxyl compounds refer to compounds capable of generating nitroxy radicals. Specific examples of N-oxyl compounds include 2,2,6,6-tetraalkylpiperidine-1-oxyl and its derivatives, such as 4-hydroxy-2,2,6,6-tetraalkylpiperidine-1-oxyl, 4-alkoxy-2,2,6,6-tetraalkylpiperidine-1-oxyl, 4-benzoyloxy-2,2,6,6-tetraalkylpiperidine-1-oxyl, and 4-amino-2,2,6,6-tetraalkylpiperidine-1-oxyl. An example of 2,2,6,6-tetraalkylpiperidine-1-oxyl is 2,2,6,6-tetramethylpiperidine-1-oxyl (also referred to as TEMPO).

[0045] The phosphate group as a modifying group can be imparted to CNF, for example, by modifying the CNF using a phosphating agent as a modifying agent.

[0046] Epoxy groups as modifying groups can be imparted to CNFs, for example, by modifying the CNFs using an epoxidizing agent such as metachloroperbenzoic acid as a modifying agent.

[0047] The ester group as the modifying group can be imparted to the CNF, for example, by modifying the CNF using an esterifying agent as a modifying agent.

[0048] Among these, CNF having a modifying group is more preferably CNF having a carboxyl group or an aldehyde group (CNF modified using an N-oxyl compound as a modifying agent) from the viewpoint of exhibiting even higher air permeation resistance.

[0049] In the rubber composition of this embodiment, the CNF content is preferably 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the rubber component. When the CNF content is 5 parts by mass or more per 100 parts by mass of the rubber component, air permeation resistance can be sufficiently improved. Furthermore, when the CNF content is 100 parts by mass or less per 100 parts by mass of the rubber component, durability can be maintained well. From the same viewpoint, the CNF content per 100 parts by mass of the rubber component is more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and more preferably 50 parts by mass or less, even more preferably 35 parts by mass or less.

[0050] (carbon black) The rubber composition of this embodiment preferably further contains carbon black. In this case, air permeability resistance can be more sufficiently improved. The carbon black is not particularly limited, and examples thereof include fossil resource-derived carbon black, plant-derived carbon black from the viewpoint of environmental impact, and recycled carbon black. Examples of fossil resource-derived carbon black include carbon black derived from hydrocarbons such as acetylene, and petroleum-derived carbon black. Examples of plant-derived carbon black include castor oil-derived carbon black and pine oil-derived carbon black. Examples of recycled carbon black include carbon black obtained by pyrolysis of used tires and carbon black obtained from waste oil. The grade of the carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N660, and N762. The carbon black may be a commercially available product, such as products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., CABOT Corporation, Birla Carbon Co., Ltd., etc. These carbon blacks may be used alone or in combination of two or more.

[0051] The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited and can be adjusted appropriately. For example, the nitrogen adsorption specific surface area (N2SA) of the carbon black is 5 m 2 / g or more is preferable, and 10m 2 / g or more is more preferable, and 20m 2 / g or more is more preferable, and 30m 2 / g or more is more preferable, and 36m 2 / g or more is more preferable, and 200m 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130 m2 / g or less is even more preferable. In this specification, the nitrogen adsorption specific surface area (N2SA) of carbon black is measured according to JIS K 6217-2:2017 (ISO 4652:2012).

[0052] The content of the carbon black is not particularly limited and can be adjusted appropriately. For example, the content of the carbon black is preferably 10 parts by mass or more, and more preferably 80 parts by mass or less, and more preferably 70 parts by mass or less, based on 100 parts by mass of the rubber component.

[0053] (silica) The rubber composition of this embodiment may further contain silica. The silica is not particularly limited, and examples thereof include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. These silicas may be used alone or in combination of two or more. Commercially available silicas may be used, including those from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, and Tokuyama Corporation.

[0054] The rubber composition of this embodiment is not particularly limited, and may contain silica derived from siliceous plants from the viewpoint of reducing environmental impact. Examples of siliceous plants include mosses, ferns, horsetails, plants of the Cucurbitaceae family, Urticaceae family, and Poaceae family. Among these plants, grasses are preferred. Examples of grasses include rice, bamboo, and sugarcane, with rice being preferred. Rice is widely cultivated for food and therefore can be procured locally over a wide area. Furthermore, rice husks are generated in large quantities as industrial waste, making them easy to secure. Therefore, from the viewpoint of availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred. The use of rice husk silica allows for the effective use of rice husks, which are otherwise industrial waste, and also allows for the local procurement of raw materials near tire manufacturing plants, thereby reducing the energy and costs involved in transportation and storage, making it environmentally preferable from various viewpoints. The rice husk silica may be a powder of rice husk charcoal obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet process using an alkali silicate aqueous solution, which is prepared by extracting rice husk ash generated when rice husks are burned as fuel in a biomass boiler with an alkali. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husk charcoal can be obtained by pyrolyzing rice husks by steaming them in a kiln. The rice husk charcoal obtained in this manner can be pulverized using a known pulverizer (e.g., a ball mill), sorted, and classified into a predetermined particle size range to obtain rice husk charcoal powder. The rice husk-derived precipitated silica can be produced by a method such as that described in JP 2019-38728 A. From the viewpoint of reducing the environmental load, it is also preferable to use, as the silica, silica obtained by extracting silicic acid components from scraps of silicon wafers, which are raw materials for semiconductors, glass bottles, etc., and recycling the extracted silica for use in the production.

[0055] The nitrogen adsorption specific surface area (N2SA) of the silica is not particularly limited and can be adjusted appropriately. For example, the nitrogen adsorption specific surface area (N2SA) of the silica is 50 m 2 / g or more is preferable, and 100m 2 / g or more is more preferable, and 150m 2 / g or more is more preferable, and 350m 2 / g or less is preferable, and 250m 2 / g or less is more preferable, and 230m 2 / g or less is more preferable, and 200m 2 / g or less is even more preferable. In this specification, the nitrogen adsorption specific surface area (N2SA) of silica is measured by the BET method in accordance with ASTM D3037-93.

[0056] (mineral filler) The rubber composition of this embodiment may contain a mineral filler. Examples of mineral fillers include clay; smectite clay minerals such as montmorillonite, saponite, hectorite, beidellite, stevensite, and nontronite; mica; feldspar; vermiculite; halloysite; and talc. However, from the viewpoint of further reducing the environmental impact, it is preferable that the rubber composition of this embodiment does not contain the above-mentioned mineral fillers. Since the rubber composition of this embodiment contains CNF, it can exhibit high air permeability resistance even without containing the above-mentioned mineral fillers.

[0057] (Other ingredients) The rubber composition of this embodiment may contain other components in addition to the rubber component, CNF, and any filler. Examples of other components include vulcanizing agents, vulcanization accelerators, silane coupling agents, vulcanization accelerator assistants, vulcanization retarders, softeners such as various process oils, zinc oxide, stearic acid, wax, antioxidants, compatibilizers, workability improvers, lubricants, tackifiers, UV absorbers, dispersants, and homogenizers. These other components may be contained in appropriate amounts.

[0058] The rubber composition of the present embodiment may contain lignin, which has been used as a filler in conventional techniques, but it does not have to contain it. The rubber composition of the present embodiment contains CNF, so that it can exhibit high air permeation resistance even without containing the above-mentioned lignin.

[0059] <Production of Rubber Composition> The rubber composition of the present embodiment can be produced by mixing the above-mentioned various components using a common rubber kneading machine, such as a Banbury mixer, kneader, or roll.

[0060] In producing a rubber composition, for example, a masterbatch can be prepared by first mixing CNF with a portion of the rubber component, and then mixing the masterbatch with the remaining rubber component and other components to produce the rubber composition. Alternatively, the rubber component, CNF, and any other components can be mixed at once without preparing a masterbatch to produce the rubber composition. In particular, from the viewpoint of producing a rubber composition with excellent air permeability resistance with high manufacturability, it is preferable to produce the rubber composition without preparing a masterbatch.

[0061] <Uses of rubber compositions> The use of the rubber composition of the present embodiment is not particularly limited, but since the rubber composition can exhibit high air permeability resistance and has good vulcanization characteristics, it is preferably used to produce an inner liner of a tire. That is, the rubber composition of the present embodiment is preferably used for an inner liner of a tire.

[0062] <Tires> A tire according to one embodiment of the present invention is characterized by including the above-described rubber composition. The tire can include a rubber member made using the above-described rubber composition. The rubber member of such a tire is not particularly limited. However, since the above-described rubber composition can exhibit high air permeation resistance and has good vulcanization characteristics, the rubber member is preferably an inner liner. [Example]

[0063] The present invention will be described in more detail below with reference to examples. However, these examples are intended to illustrate the present invention and are not intended to limit the present invention in any way.

[0064] (Preparation of Rubber Composition) In each example, a rubber composition was prepared according to a conventional method using the compounding recipe shown in Table 1. Then, the rubber composition was vulcanized at 145°C for 45 minutes to obtain a vulcanized rubber.

[0065] <Evaluation of vulcanization characteristics> Vulcanization curves were obtained using a Curastometer (registered trademark) (manufactured by JSR Corporation) for the rubber compositions of Reference Example 1, Comparative Example 1, and Example 1. The vulcanization curves are shown in Figure 1. The sharper the rise in the vulcanization curve (the greater the slope), the better the vulcanization characteristics.

[0066] <Evaluation of air permeability resistance> For each vulcanized rubber, the oxygen permeability coefficient (unit: cc cm / cm) was measured using a GTR-31ABSM permeability measuring instrument manufactured by GTR Tech Co., Ltd. in accordance with JIS K 6275-1:2009. 2 The oxygen permeability coefficient (sec cmHg) was measured. The results are shown in Table 1. The smaller the measured oxygen permeability coefficient, the better the resistance to air permeation. Similarly, for each vulcanized rubber, the nitrogen permeability coefficient (unit: cc cm / cm) was measured using a GTR-31ABSM permeability measuring instrument manufactured by GTR Tech Co., Ltd. in accordance with JIS K 6275-1:2009. 2 The results are shown in Table 1. The smaller the measured nitrogen permeability coefficient, the better the air permeability resistance.

[0067] [Table 1]

[0068] *1 Butyl rubber: Exxon "Bromobutyl 2255" *2 Clay: BASF "ASP NC X-1" *3 Lignin: UPM4000 manufactured by UPM *4 CNF1: Cellulose Lab, "Carboxymethylated Cellulose Nanofibrils, Spray-dried, Pulp material", carboxymethylated cellulose nanofiber, average diameter: 10-13 nm, average length: 1000-3000 nm, aspect ratio: over 76 *5 CNF2: Cellulose Lab's "TEMPO (Anionic type) Cellulose Nanofibrils Powder", cellulose nanofibers modified with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), average diameter: 50 nm, average length: 0.5 μm to 80 μm, aspect ratio: 10 or more *6 Carbon black: CABOT "STERLING V"

[0069] 1, it can be seen that the vulcanization curve of Comparative Example 1 using lignin has a gradual rise, unlike Reference Example 1 using clay, and therefore has poor vulcanization characteristics. In contrast, the vulcanization curve of Example 1 using CNF has a sharp rise, similar to Reference Example 1 using clay, and therefore has good vulcanization characteristics.

[0070] Table 1 also shows that the rubber compositions (vulcanized rubbers) of the Examples using CNF all have smaller oxygen permeability coefficients and equal or smaller nitrogen permeability coefficients than the rubber composition of Reference Example 1 using clay. Furthermore, the rubber compositions (vulcanized rubbers) of the Examples using CNF all have smaller oxygen and nitrogen permeability coefficients than the rubber composition of Comparative Example 1 using lignin. This means that the rubber compositions (vulcanized rubbers) of the Examples using CNF can exhibit high air permeability resistance. [Industrial Applicability]

[0071] According to the present invention, it is possible to provide a rubber composition that has a small environmental impact, exhibits high air permeation resistance, and has good vulcanization characteristics, and a tire using the same.

Claims

1. A rubber composition comprising a rubber component containing a butyl-based rubber and cellulose nanofibers.

2. The rubber composition according to claim 1 , wherein the cellulose nanofibers have an aspect ratio of 3 or more.

3. The rubber composition according to claim 1 or 2, wherein the cellulose nanofiber has a modifying group.

4. The rubber composition according to claim 1 or 2, wherein an amount of the cellulose nanofibers is 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the rubber component.

5. The rubber composition according to claim 1 or 2, further comprising carbon black.

6. The rubber composition according to claim 1 or 2, wherein the content of the natural rubber is less than twice the content of the cellulose nanofibers.

7. The rubber composition according to claim 1 or 2, wherein the proportion of the isoprene-based rubber in the rubber component is less than 5% by mass.

8. The rubber composition according to claim 1 or 2, which is used for an inner liner of a tire.

9. A tire comprising the rubber composition according to claim 1 or 2.

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