RFID-tag coating rubber composition, and tire

Abstract

The present invention addresses the problem of providing an RFID-tag coating rubber composition that can achieve a good balance among communication performance, resistance to cracking, adhesiveness to an adjacent rubber member, and elastic modulus. The solution to said problem is an RFID-tag coating rubber composition characterized by including a rubber component and silica, wherein the silica content is 60 parts by mass or more with respect to 100 parts by mass of the rubber component. The RFID-tag coating rubber composition preferably further includes a silane coupling agent.

Description

Coating rubber composition for RFID tags and tires

[0001] The present invention relates to a coating rubber composition for an RFID tag and a tire.

[0002] It has been proposed to individually manage tires by attaching an RFID (Radio Frequency Identification) tag to a tire and writing or reading various information about the tire, such as its manufacturing history, distribution history, and usage history, to or from the RFID tag (Patent Document 1). The RFID tag is typically covered with a coating rubber to be disposed inside a tire made primarily of rubber. The coating rubber for the RFID tag must have various required properties, such as communication performance, crack resistance, adhesion to adjacent rubber members, and an appropriate elastic modulus.

[0003] EP 1580041

[0004] Under these circumstances, the inventors investigated conventional coating rubbers for RFID tags and found that it was difficult to achieve a satisfactory balance between communication performance, crack resistance, adhesion to adjacent rubber members, and elastic modulus with conventional coating rubbers for RFID tags.

[0005] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a coating rubber composition for RFID tags that can sufficiently balance communication performance, crack resistance, adhesion to adjacent rubber members, and elastic modulus.A further object of the present invention is to provide a tire equipped with an RFID tag that has excellent communication performance and durability.

[0006] The coating rubber composition for RFID tags and the tire of the present invention that solve the above problems are outlined below.

[0007] [1] A coating rubber composition for RFID tags, comprising a rubber component and silica, wherein the content of the silica is 60 parts by mass or more per 100 parts by mass of the rubber component.

[0008] [2] The coating rubber composition for RFID tags according to [1], further comprising a silane coupling agent.

[0009] [3] The coating rubber composition for RFID tags according to [2], wherein the content of the silane coupling agent is 5 to 20 mass % of the content of the silica.

[0010] [4] The coating rubber composition for RFID tags according to any one of [1] to [3], wherein the content of the silica is 60 to 100 parts by mass, more preferably 60 to 80 parts by mass, per 100 parts by mass of the rubber component.

[0011] [5] A tire comprising an RFID tag coated with the coating rubber composition for RFID tags according to any one of [1] to [4].

[0012] According to the present invention, it is possible to provide a coating rubber composition for RFID tags that can satisfactorily balance communication performance, crack resistance, adhesion to adjacent rubber members, and elastic modulus, and also to provide a tire that is excellent in communication performance and durability.

[0013] 1 is a cross-sectional view of one embodiment of a tire of the present invention.

[0014] The coating rubber composition for RFID tags and the tire of the present invention will be described in detail below by way of example based on embodiments thereof.

[0015] <Coating Rubber Composition for RFID Tags> The coating rubber composition for RFID tags of the present invention includes a rubber component and silica. Here, the coating rubber composition for RFID tags of the present invention is characterized in that the content of the silica is 60 parts by mass or more per 100 parts by mass of the rubber component.

[0016] Typical rubber compositions contain carbon black, which increases the dielectric constant of the rubber composition, shortening the communication distance (communicable distance) of RFID tags and reducing communication performance. Without carbon black, the crack resistance and modulus of elasticity of the rubber composition decrease. In contrast, the coating rubber composition for RFID tags of the present invention contains silica, which, unlike carbon black, does not increase the dielectric constant of the rubber composition, thereby extending the communication distance of RFID tags and improving communication performance. Furthermore, by containing silica in an amount of 60 parts by mass or more per 100 parts by mass of the rubber component, the crack resistance and modulus of elasticity of the rubber composition can be sufficiently ensured. Furthermore, by having a sufficient modulus of elasticity of the rubber composition, stress concentration on the RFID tag coated with the rubber composition can be suppressed, ensuring adhesion between the rubber composition (coating) and adjacent rubber members. Therefore, the coating rubber composition for RFID tags of the present invention can achieve a sufficient balance of communication performance, crack resistance, adhesion to adjacent rubber members, and modulus of elasticity.

[0017] (Rubber Component) The coating rubber composition for RFID tags of the present invention contains a rubber component, which provides rubber elasticity to the composition. The rubber component is preferably a diene rubber, and may be natural rubber (NR), synthetic diene rubber, or both. Examples of the synthetic diene rubber include isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene rubber (SIR), and chloroprene rubber (CR). The rubber component may be a single type or a blend of two or more types.

[0018] (Silica) The coating rubber composition for RFID tags of the present invention contains silica, and the content of the silica is 60 parts by mass or more per 100 parts by mass of the rubber component. By blending silica into the rubber composition, the crack resistance and elastic modulus of the rubber composition can be improved without increasing the relative dielectric constant of the rubber composition. However, if the content of silica is less than 60 parts by mass per 100 parts by mass of the rubber component, the crack resistance and elastic modulus of the rubber composition are insufficient. Note that, from the viewpoint of the communication distance (communicable distance) of the RFID tag, the relative dielectric constant of the rubber composition is preferably 4.0 or less, more preferably 2.5 or less.

[0019] Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate, and among these, wet silica is preferred. These silicas may be used alone or in combination of two or more.

[0020] The content of the silica is preferably 60 to 100 parts by mass, more preferably 60 to 80 parts by mass, per 100 parts by mass of the rubber component. When the content of silica is 60 parts by mass or more per 100 parts by mass of the rubber component, the crack resistance and elastic modulus of the rubber composition can be further improved. When the content of silica is less than 60 parts by mass per 100 parts by mass of the rubber component, the crack resistance and elastic modulus of the rubber composition decrease. When the content of silica is 60 to 100 parts by mass per 100 parts by mass of the rubber component, the crack resistance and elastic modulus of the rubber composition can be further improved. When the content of silica is 60 to 80 parts by mass per 100 parts by mass of the rubber component, the crack resistance and elastic modulus of the rubber composition can be further improved.

[0021] (Silane Coupling Agent) The coating rubber composition for RFID tags of the present invention preferably further contains a silane coupling agent. When the rubber composition contains a silane coupling agent, the interaction between the rubber component and silica increases, improving the dispersibility of silica in the rubber component. Furthermore, the improved dispersibility of silica in the rubber component allows the silica to fully exert its effects, further improving the crack resistance and elastic modulus of the rubber composition.

[0022] Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N , N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, etc. These silane coupling agents may be used alone or in combination of two or more.

[0023] The content of the silane coupling agent is preferably 5 to 20% by mass of the content of the silica (i.e., 5 to 20 parts by mass per 100 parts by mass of silica). When the content of the silane coupling agent is 5% by mass or more of the content of the silica, the compounding effect of the silane coupling agent is increased, the dispersibility of the silica in the rubber component is further improved, and the crack resistance and elastic modulus of the rubber composition can be further improved. Furthermore, when the content of the silane coupling agent is 20% by mass or less of the content of the silica, gelation of the rubber component can be suppressed. Note that when the content of the silane coupling agent is 5 to 20% by mass of the content of the silica, the crack resistance and elastic modulus of the rubber composition can be further improved.

[0024] (Others) The coating rubber composition for RFID tags of the present invention preferably contains a vulcanizing agent, a vulcanization accelerator, oil, and a tackifier in addition to the above-mentioned rubber component, silica, and silane coupling agent. Furthermore, the coating rubber composition for RFID tags of the present invention may further contain various components commonly used in the rubber industry, as needed, such as fillers other than silica, antioxidants, waxes, softeners other than oils, processing aids, stearic acid, zinc oxide (zinc oxide), and the like, appropriately selected within a range that does not impair the object of the present invention. Commercially available products can be suitably used as these compounding ingredients.

[0025] The rubber composition containing a vulcanizing agent can be vulcanized, improving the crack resistance and elastic modulus of the rubber composition. Examples of the vulcanizing agent include sulfur. Here, the sulfur preferably contains insoluble sulfur. Insoluble sulfur is sulfur that is insoluble in carbon disulfide (amorphous polymeric sulfur), and is less soluble in rubber components than soluble sulfur, making it less likely to cause blooming. From the viewpoint of further improving workability during tire molding, the proportion of insoluble sulfur in the sulfur is preferably 50 to 90% by mass. From the viewpoint of further improving the crack resistance and elastic modulus of the rubber composition, the content of the vulcanizing agent is preferably 6.0 parts by mass or more per 100 parts by mass of the rubber component.

[0026] By including a vulcanization accelerator in the rubber composition, the vulcanization rate can be increased, thereby improving the modulus of elasticity of the rubber composition. Examples of vulcanization accelerators include guanidine-based vulcanization accelerators, sulfenamide-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiuram-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators. Among these, guanidine-based vulcanization accelerators are preferred. Furthermore, among guanidine-based vulcanization accelerators, 1,3-diphenylguanidine (DPG) is particularly preferred. From the viewpoint of increasing the vulcanization rate of the rubber composition and further improving the modulus of elasticity of the rubber composition, the content of the vulcanization accelerator is preferably 0.0 to 1.0 part by mass per 100 parts by mass of the rubber component.

[0027] When the rubber composition contains oil, the rubber composition is better held together during kneading, improving workability during kneading. The oil is a general term for extender oil contained in the rubber component and liquid oil added as a compounding agent to the rubber composition, and examples thereof include petroleum-based softeners such as aromatic oil, paraffinic oil, and naphthenic oil; and plant-based softeners such as palm oil, castor oil, cottonseed oil, and soybean oil. Among these, petroleum-based softeners such as aromatic oil, paraffinic oil, and naphthenic oil are preferred.

[0028] The oil is preferably a naphthenic oil containing asphalt. When the rubber composition contains a naphthenic oil containing asphalt, the rubber composition is further improved in cohesion during kneading, further improving workability during kneading. The naphthenic oil containing asphalt is preferably a mixture of naphthenic base oil and asphalt in a mass ratio range of (95 / 5) to (30 / 70). This mass ratio range further improves compatibility between the rubber component and the oil. The naphthenic base oil is preferably a hydrogenated naphthenic base oil, and particularly preferably a hydrogenated naphthenic base oil obtained by subjecting aromatic oils or naphthenic oils to advanced hydrorefining using a high-pressure, high-temperature hydrorefining production unit. Specifically, such hydrogenated naphthenic base oils are commercially available as products such as SNH8, SNH46, SNH220, and SNH440 (all trademarks) manufactured by Sankyo Yuka Kogyo Co., Ltd. Furthermore, in consideration of compatibility with the rubber components used and the effect of improving the cohesion of the rubber composition during kneading, it is preferable that the asphalt to be mixed with the naphthenic base oil contains an asphaltene component of 5% by mass or less. The asphaltene component is quantified by composition analysis measured in accordance with the JPI method [Japan Petroleum Institute Standard JPI-5S-22-83 (established in 1983) standard name "Asphalt Composition Analysis Method by Column Chromatography"]. Such asphalt is preferably straight asphalt, and particularly preferably naphthenic straight asphalt. Furthermore, the asphalt has a kinematic viscosity at 120°C of 300 mm ２ / second or less is preferable. The method for mixing the asphalt is not particularly limited, but from the viewpoints of ease of preparation and economy, a method of preparing the asphalt by dissolving the asphalt in a naphthenic base oil (including extender oil and blending oil) is preferable. As the naphthenic oil containing the asphalt, a product name "A / O Mix" manufactured by Sankyo Yuka Kogyo Co., Ltd. is preferable, which is obtained by mixing a hydrogenated naphthenic base oil produced by a high-pressure, high-temperature hydrorefining unit with a naphthenic straight asphalt containing 5% by mass or less of asphaltene in a mass ratio of 63 / 37. From the viewpoints of further improving the cohesion of the rubber composition during kneading and further improving workability during kneading, the content of the oil is preferably more than 0 parts by mass and 15 parts by mass or less per 100 parts by mass of the rubber component.

[0029] When the rubber composition contains a tackifier, the adhesiveness of the rubber composition is improved, and the workability of the rubber composition during tire molding is improved. Various natural and synthetic resins can be used as the tackifier, and specifically, rosin-based resins, terpene-based resins, petroleum-based resins, phenol-based resins, coal-based resins, and xylene-based resins are preferably used. These tackifiers may be used alone or in combination of two or more. When the rubber composition contains at least one resin selected from the group consisting of rosin-based resins, terpene-based resins, petroleum-based resins, phenol-based resins, coal-based resins, and xylene-based resins, the adhesiveness of the rubber composition is further improved, and the workability of the rubber composition during tire molding is further improved.

[0030] Among the natural resins, examples of rosin-based resins include gum rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, glycerin and pentaerythritol esters of modified rosin, etc. Furthermore, examples of terpene-based resins among the natural resins include α-pinene-based, β-pinene-based, and dipentene-based terpene resins, aromatic modified terpene resins, terpene phenolic resins, and hydrogenated terpene resins, etc. Among these natural resins, polymerized rosin, terpene phenolic resins, and hydrogenated terpene resins are preferred from the viewpoint of the fracture resistance of the rubber composition blended therewith.

[0031] Among the synthetic resins, the petroleum-based resins are obtained by polymerizing a mixture of cracked oil fractions containing unsaturated hydrocarbons such as olefins and diolefins, which are by-produced together with petrochemical base materials such as ethylene and propylene, by thermal decomposition of naphtha in the petrochemical industry, using a Friedel-Crafts catalyst. ５ Aliphatic petroleum resin (hereinafter referred to as "C") obtained by (co)polymerizing the fraction ５ C-based resins are sometimes called "carbon-based resins" and are obtained by thermal decomposition of naphtha. ９ Aromatic petroleum resin (hereinafter referred to as "C") obtained by (co)polymerizing the fraction ９ (sometimes referred to as "a-type resin").) ５ Fraction and C ９ Copolymerized petroleum resin (hereinafter referred to as "C") obtained by copolymerizing the fraction ５ -C ９ These include alicyclic compound-based petroleum resins such as hydrogenated and dicyclopentadiene-based resins, and styrene-based resins such as copolymers of styrene, substituted styrene, or styrene with other monomers.

[0032] C obtained by thermal cracking of naphtha ５ The fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. ９ Aromatic petroleum resins obtained by copolymerizing the fraction are resins polymerized from aromatics with 9 carbon atoms, with vinyltoluene and indene as the main monomers, and are also C4 obtained by thermal cracking of naphtha. ９ Specific examples of the fraction include styrene homologues such as α-methylstyrene, β-methylstyrene, and γ-methylstyrene, and indene homologues such as indene and coumarone. Trade names include Petrogin manufactured by Mitsui Petrochemicals, Petrite manufactured by Mikuni Chemicals, Neopolymer manufactured by Nippon Petrochemicals, and Petcol manufactured by Toyo Soda.

[0033] Furthermore, from the viewpoint of workability,９ Modified petroleum resins obtained by modifying petroleum resins made from fractions can be preferably used. The modified petroleum resins include C 2 modified with unsaturated alicyclic compounds. ９ C modified with petroleum resin and compounds containing hydroxyl groups ９ C modified with unsaturated carboxylic acid compound ９ petroleum resins and the like.

[0034] Preferred unsaturated alicyclic compounds include cyclopentadiene, methylcyclopentadiene, etc. Furthermore, as the unsaturated alicyclic compound, Diels-Alder reaction products of alkylcyclopentadiene are also preferred, and examples of the Diels-Alder reaction products of alkylcyclopentadiene include dicyclopentadiene, cyclopentadiene / methylcyclopentadiene co-dimer, tricyclopentadiene, etc. As the unsaturated alicyclic compound, dicyclopentadiene is particularly preferred. Dicyclopentadiene-modified C ９ The petroleum resin is made of dicyclopentadiene and C ９ The dicyclopentadiene-modified C can be obtained by thermal polymerization in the presence of both fractions. ９ An example of a petroleum-based resin is Neopolymer 130S (manufactured by Nippon Petrochemical Co., Ltd.).

[0035] Examples of compounds having a hydroxyl group include alcohol compounds and phenol compounds. Specific examples of alcohol compounds include alcohol compounds having a double bond, such as allyl alcohol and 2-butene-1,4-diol. Examples of phenol compounds that can be used include alkylphenols such as phenol, cresol, xylenol, p-tert-butylphenol, p-octylphenol, and p-nonylphenol. These compounds having a hydroxyl group may be used alone or in combination of two or more. Specific examples of C ９ The petroleum resins can be produced by a method in which an alkyl (meth)acrylate ester or the like is thermally polymerized with a petroleum fraction to introduce an ester group into the petroleum resin, and then the ester group is reduced, or by a method in which a double bond is left or introduced into the petroleum resin, and then the double bond is hydrated.９ As the petroleum resin, those obtained by various methods as described above can be used, but from the viewpoints of performance and production, it is preferable to use phenol-modified petroleum resins. ９ The phenol-modified C is obtained by cationic polymerization of the fraction in the presence of phenol, and is easy to modify and inexpensive. ９ An example of a petroleum-based resin is Neopolymer E-130 (manufactured by Nippon Petrochemical Co., Ltd.).

[0036] Furthermore, the C modified with the unsaturated carboxylic acid compound ９ C-based petroleum resins ９ The petroleum resin can be modified with an ethylenically unsaturated carboxylic acid. Representative examples of such ethylenically unsaturated carboxylic acids include maleic acid (anhydride), fumaric acid, itaconic acid, tetrahydrophthalic acid (anhydride), (meth)acrylic acid, and citraconic acid. ９ C-based petroleum resins ９ The maleic acid-modified C can be obtained by thermally polymerizing a maleic acid-modified petroleum resin and an ethylenically unsaturated carboxylic acid. ９ Petroleum resins based on unsaturated carboxylic acid are preferred. ９ An example of a petroleum-based resin is Neopolymer 160 (manufactured by Nippon Petrochemical Co., Ltd.).

[0037] Also, C obtained by thermal cracking of naphtha ５ Fraction and C ９ The copolymer resin of the fraction can be suitably used. ９ The fraction is not particularly limited, but may be C obtained by thermal cracking of naphtha. ９ Specific examples include TS30, TS30-DL, TS35, and TS35-DL of the Struktol series manufactured by Schill & Seilacher.

[0038] Among the synthetic resins, examples of the phenolic resin include alkylphenol formaldehyde resins and rosin-modified versions thereof, alkylphenol acetylene resins, modified alkylphenol resins, and terpene phenol resins. Specific examples include Hitanol 1502 (manufactured by Hitachi Chemical Co., Ltd.), a novolac alkylphenol resin, and Cholesin (manufactured by BASF), a p-tert-butylphenol acetylene resin.

[0039] Among the synthetic resins, examples of the coal-based resins include coumarone-indene resins, and examples of the xylene-based resins include xylene-formaldehyde resins. In addition, polybutene can also be used as a resin having tackifying properties.

[0040] From the viewpoint of further improving the adhesiveness of the rubber composition and further improving workability during tire molding, the content of the tackifier is preferably more than 0 part by mass and not more than 15 parts by mass per 100 parts by mass of the rubber component.

[0041] The coating rubber composition for RFID tags of the present invention may or may not contain carbon black as a filler other than silica. Here, the content of carbon black is preferably 20 parts by mass or less per 100 parts by mass of the rubber component, and particularly preferably 0 parts by mass (i.e., no carbon black is contained). When the content of carbon black is 20 parts by mass or less per 100 parts by mass of the rubber component, the relative dielectric constant of the rubber composition decreases, thereby increasing the communication distance of the RFID tag. When the content of carbon black is 0 parts by mass (i.e., no carbon black is contained), the relative dielectric constant of the rubber composition further decreases, thereby further increasing the communication distance of the RFID tag.

[0042] (Method for Producing Rubber Composition) The method for producing the rubber composition is not particularly limited, but the rubber composition can be produced, for example, by blending the above-mentioned rubber component and silica with various components appropriately selected as necessary, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0043] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0044] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roll mill typically used for heat-in of rubber compositions.

[0045] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0046] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of vulcanization apparatus include a molding vulcanizer using a mold used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.

[0047] <Tire> The tire of the present invention is characterized by including an RFID tag coated with the above-mentioned coating rubber composition for RFID tags. Because the tire of the present invention includes an RFID tag coated with the above-mentioned coating rubber composition for RFID tags, it has excellent communication performance and durability.

[0048] The RFID tag is generally made of a material such as metal or resin. For example, in one embodiment, the RFID tag comprises an electronic device portion and an antenna portion connected to the electronic device portion, with the housing (or package) of the electronic device portion being made of resin and the antenna portion being made of metal. Here, when coating the RFID tag with the above-mentioned coating rubber composition for RFID tags of the present invention, sufficient adhesion between the RFID tag and the coating rubber can be ensured by previously applying an adhesive such as "CHEMLOC" (registered trademark) manufactured by LORD Corporation to the RFID tag.

[0049] Furthermore, since the RFID tag is harder than the rubber members in the tire, in order to prevent stress from concentrating on the RFID tag, it is preferable that the coating rubber of the RFID tag has a higher elastic modulus (i.e., is harder) than the adjacent rubber members (for example, the side rubber, stiffener, etc., which will be described later). The above-mentioned coating rubber composition for RFID tags has a high elastic modulus and is hard, and therefore also has the effect of preventing stress from concentrating on the RFID tag.

[0050] The RFID tag is preferably disposed in a portion of the tire that is relatively little strained during running. In one embodiment, the RFID tag coated with the above-mentioned coating rubber composition for RFID tags is preferably disposed between a stiffener disposed radially outward of a bead core embedded in a bead portion of the tire and a side rubber located on the outer side of a carcass in a side portion of the tire in the tire width direction. In this embodiment, it is further preferable that the RFID tag coated with the coating rubber composition for RFID tags is disposed in a portion radially inward of the maximum width portion of the tire.

[0051] Figure 1 is a cross-sectional view of one embodiment of a tire of the present invention. The tire 1 shown in Figure 1 has a pair of bead portions 2, a pair of side portions 3, and a tread portion 4 connected to both side portions 3. The tire 1 is equipped with a carcass 5 extending toroidally between the pair of bead portions 2 to reinforce these portions 2, 3, and 4, a belt 6 disposed radially outward of a crown portion of the carcass 5, and stiffeners 8 disposed radially outward of ring-shaped bead cores 7 embedded in the bead portions 2. The stiffeners 8 are composed of a hard stiffener 8a with relatively high rigidity adjacent to the bead core 7 on the radially outer side, and a soft stiffener 8b with relatively low rigidity adjacent to the hard stiffener 8a on the radially outer side. A side rubber 9 is disposed on the side portion 3 on the outer side of the carcass 5 in the tire width direction.

[0052] In the tire 1 shown in the figure, the carcass 5 has a main body portion 5a extending toroidally between a pair of bead cores 7, and turned-up portions 5b wound up radially outward from the inner side toward the outer side in the tire width direction around each bead core 7. Note that the structure and number of plies of the carcass 5 are not limited to this. A stiffener 8 is disposed between the main body portion 5a of the carcass 5 and the turned-up portion 5b. A wire chafer 10 is disposed on the outer surface side of the turned-up portion 5b of the carcass 5, and the wire chafer 10 further extends along the outer side of the stiffener 8 in the tire width direction.

[0053] Furthermore, an RFID tag 12 coated with coating rubber 11 is disposed in a region radially inward of the maximum width portion of the tire, between the side rubber 9 and the soft stiffener 8b, and radially outward of the wire chafer 10. The coating rubber 11 uses the above-described coating rubber composition for RFID tags. The RFID tag 12 coated with coating rubber 11 (RFID tag-rubber composite) can be produced, for example, by preparing two rubber sheets made of the above-described coating rubber composition for RFID tags and sandwiching the RFID tag 12 between the rubber sheets. The tire of this embodiment can be produced by laminating the RFID tag-rubber composite with other rubber members to form a green tire, and then vulcanizing the green tire.

[0054] As described above, the rubber composition used in the coating rubber 11 has good communication performance, so the tire 1 shown in Fig. 1 has a long communication distance and excellent communication performance. Also, as described above, the rubber composition used in the coating rubber 11 has a sufficient balance of crack resistance, adhesion to adjacent rubber members, and elastic modulus, so the tire 1 shown in Fig. 1 has excellent durability.

[0055] The tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire to be applied, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization step or the like and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0056] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0057] <Preparation of Rubber Compositions> According to the formulations shown in Tables 1 and 2, the ingredients (excluding the vulcanization accelerator, vulcanizing agent, and other Pro-chemicals) were filled to a filling rate of 55% to 65% using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd., and mixed at 80 rpm until the temperature reached 160°C or 4 minutes had elapsed. Next, the vulcanization accelerator, vulcanizing agent, and other Pro-chemicals were added to the resulting mixture in the amounts shown in Tables 1 and 2, and the mixture was mixed using an open roll at 80°C for 2 minutes to obtain unvulcanized rubber compositions according to the formulations of each Example and Comparative Example. Furthermore, plate-shaped samples of the crosslinked rubber compositions were produced by vulcanizing the unvulcanized rubber compositions at 145°C for 45 minutes.

[0058] <Evaluation of Rubber Compositions> The rubber compositions obtained in the examples and comparative examples were evaluated for communication performance, crack resistance, adhesion to adjacent rubber members, and elastic modulus by the following methods. The results are shown in Tables 1 and 2.

[0059] (1) Communication performance: The relative permittivity of the vulcanized rubber composition plate sample is measured at 860 MHz using a relative permittivity meter. From past measurements of the relative permittivity, it is known that the relative permittivity can be estimated from the amount of carbon black in the rubber compound. Therefore, the relative permittivity is calculated.

[0060] (2) Crack Resistance A vulcanized rubber test piece was processed into a 2 mm thick JIS No. 5 type test piece, and a 0.5 mm crack was made in the center of the test piece. Both ends of the test piece were gripped and repeatedly subjected to input under the following conditions, and the number of times until the test piece broke was measured. Test stress: 1.9 N m Frequency: 5 Hz Ambient temperature: 80°C The table shows the number of times until breakage, rounded to the nearest hundred. The higher the number of times until breakage, the better the crack growth resistance of the test piece, and this means that a prototype tire made of the vulcanized rubber of the test piece has excellent crack growth resistance. If the number of times until breakage is 10,000 or more, it can be said that the crack growth resistance is excellent.

[0061] (3) Durability Evaluation (E') Using a spectrometer (manufactured by Ueshima Seisakusho Co., Ltd.), the dynamic modulus of elasticity (E') was measured under conditions of a temperature of 24°C, a strain of 1%, and a frequency of 52 Hz. The higher the dynamic modulus of elasticity (E'), the harder the rubber is and the less likely it is to deform, indicating superior durability, and therefore indicating that a tire made of the vulcanized rubber test piece has excellent durability. Furthermore, vulcanized rubber with a high dynamic modulus of elasticity (E') can suppress stress concentration on the RFID tag and ensure adhesion to adjacent rubber members.

[0062] (4) Tensile Strength (TB) and Modulus of Elasticity (M100) The tensile strength (TB) and 100% modulus value (M100) of the vulcanized rubber test specimen were measured. The tensile strength (TB) was measured in accordance with JIS K 6251 (2017) as the maximum tensile force (MPa) required to break a 2 mm thick vulcanized rubber test specimen after 100% elongation at 25 ° C. The 100% modulus value (M100) was measured in accordance with JIS K 6251 (2017) as the modulus tensile modulus (MPa) when a 2 mm thick vulcanized rubber test specimen was elongated 100% at 25 ° C. The higher the modulus of elasticity (M100), the less likely it is to deform, which means that the durability is excellent, and therefore the tire made of the vulcanized rubber test specimen is excellent in durability. Furthermore, vulcanized rubber with a high modulus of elasticity (M100) can suppress stress concentration on the RFID tag and ensure adhesion to adjacent rubber members.

[0063]

[0064]

[0065] *1 Natural rubber: RSS #3 *2 Silica: Tosoh Silica Corporation, trade name "Nipsil AQ" *3 Carbon black (N660): Cabot Corporation, trade name "STERLING V" *4 Carbon black (N330): Cabot Corporation, trade name "VULCAN 3" *5 Silane coupling agent: Bis(3-triethoxysilylpropyl) disulfide (average sulfur chain length: 2.35), Evonik Corporation, trade name "Si75" *6 Oil: Sankyo Yuka Kogyo Co., Ltd., trade name "A / O Mix", naphthenic oil containing asphalt *7 Tackifier: SI Group RIBECOURT S.A.S. Co., Ltd., trade name "R7510PJ" * 8 Vulcanization accelerator DPG: 1,3-diphenylguanidine, Sanshin Chemical Industry Co., Ltd., trade name "Suncerer D" * 9 Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazolyl sulfenamide, Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noccela CZ-G" * 10 Vulcanization accelerator TBzTD: Tetrabenzyl thiuram disulfide, Sanshin Chemical Industry Co., Ltd., trade name "Suncerer TBZTD" * 11 Ordinary sulfur: Sulfur not containing insoluble sulfur, Tsurumi Chemical Industry Co., Ltd., trade name "Sulfax 5" * 12 Insoluble sulfur: Sulfur containing insoluble sulfur, Sanshin Chemical Industry Co., Ltd., trade name "Sunfer Ex", proportion of insoluble sulfur in sulfur = 90 mass%

[0066] It can be seen from Tables 1 and 2 that the rubber compositions of the examples according to the present invention are capable of achieving a sufficient balance of communication performance, crack resistance, adhesion to adjacent rubber members, and elastic modulus.

[0067] 1: Tire, 2: Bead portion, 3: Side portion, 4: Tread portion, 5: Carcass, 5a: Main body portion of carcass, 5b: Folded portion of carcass, 6: Belt, 7: Bead core, 8: Stiffener, 8a: Hard stiffener, 8b: Soft stiffener, 9: Side rubber, 10: Wire chafer, 11: Coating rubber, 12: RFID tag

Claims

1. The rubber composition includes a rubber component and silica, A coating rubber composition for RFID tags, characterized in that the content of the silica is 60 parts by mass or more per 100 parts by mass of the rubber component.

2. The coating rubber composition for RFID tags according to claim 1, further comprising a silane coupling agent.

3. 3. The coating rubber composition for RFID tags according to claim 2, wherein the content of the silane coupling agent is 5 to 20% by mass of the content of the silica.

4. 2. The coating rubber composition for RFID tags according to claim 1, wherein the content of said silica is 60 to 80 parts by mass per 100 parts by mass of said rubber component.

5. A tire characterized by having an RFID tag coated with the coating rubber composition for RFID tags described in claim 1.