Rubber coating composition for RFID tags and tires

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, and also has excellent workability. The solution to said problem is an RFID-tag coating rubber composition characterized by including a rubber component, sulfur, silica, and a guanidine-based vulcanization accelerator, wherein said sulfur includes insoluble sulfur, and said sulfur content is 6.0 parts by mass or more with respect to 100 parts by mass of the rubber component.

Description

Technical Field

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

Background Art

[0002] Conventionally, it has been proposed to dispose an RFID (Radio Frequency Identification) tag on a tire and write or read various information such as the manufacturing history, distribution history, and usage history of the tire to the RFID to manage the tire individually (Patent Document 1). The RFID tag is usually coated with a coating rubber in order to be disposed in a tire mainly composed of a rubber member. And the coating rubber for the RFID tag has various required characteristics such as crack resistance, adhesion to an adjacent rubber member, and an appropriate elastic modulus in addition to communication performance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] ]] Under such circumstances, when the inventor examined the conventional coating rubber for RFID tags, it was found that it is difficult to sufficiently balance the communication performance, crack resistance, adhesion to an adjacent rubber member, and elastic modulus in the conventional coating rubber for RFID tags. On the other hand, for example, when the content of sulfur blended in the rubber composition for the coating rubber is increased in order to improve the elastic modulus of the coating rubber, sulfur blooms, the adhesiveness of the rubber composition decreases, and problems such as deterioration of workability in tire molding occur.

[0005] Therefore, the present invention aims to solve the problems of the above-mentioned prior art and provide a coating rubber composition for RFID tags that can sufficiently balance communication performance, crack resistance, adhesion to adjacent rubber members, and elastic modulus, as well as having excellent workability. Furthermore, a further objective of the present invention is to provide a tire equipped with an RFID tag that is superior in communication performance, durability, and productivity. [Means for solving the problem]

[0006] The essential structure of the RFID tag coating rubber composition and tire of the present invention, which solves the above problems, is as follows.

[0007] [1] Contains rubber components, sulfur, silica, and a guanidine-based vulcanization accelerator. The sulfur includes insoluble sulfur, A coating rubber composition for RFID tags, characterized in that the sulfur content is 6.0 parts by mass or more per 100 parts by mass of the rubber component.

[0008] [2] The RFID tag coating rubber composition according to [1], wherein the silica content is 40 to 100 parts by mass per 100 parts by mass of the rubber component.

[0009] [3] The RFID tag coating rubber composition according to [1] or [2], wherein the sulfur content is 6.5 parts by mass or more, more preferably 6.8 parts by mass or more, per 100 parts by mass of the rubber component.

[0010] [4] The RFID tag coating rubber composition according to any one of [1] to [3], wherein the content of the guanidine-based vulcanization accelerator is 0.1 to 1.0 parts by mass per 100 parts by mass of the rubber component.

[0011] [5] The RFID tag coating rubber composition according to any one of [1] to [4], wherein the proportion of the insoluble sulfur in the sulfur is 50 to 90% by mass.

[0012] [6] The coating rubber composition for an RFID tag according to any one of [1] to [5], wherein the guanidine-based vulcanization accelerator is 1,3-diphenylguanidine (DPG).

[0013] [7] A tire comprising an RFID tag coated with the coating rubber composition for an RFID tag according to any one of [1] to [6].

Effects of the Invention

[0014] According to the present invention, it is possible to provide a coating rubber composition for an RFID tag that can sufficiently balance communication performance, crack resistance, adhesion to an adjacent rubber member, and elastic modulus, and is also excellent in workability. Further, according to the present invention, it is possible to provide a tire excellent in communication performance, durability, and productivity. [[ID=****]]

Brief Description of the Drawings

[0015] [Figure 1] [[ID=2**]]A cross-sectional view of an embodiment of the tire of the present invention.

Modes for Carrying Out the Invention

[0016] Hereinafter, the coating rubber composition for an RFID tag and the tire of the present invention will be specifically illustrated and described based on their embodiments.

[0017] <Coating Rubber Composition for RFID Tag> The coating rubber composition for an RFID tag of the present invention contains a rubber component, sulfur, silica, and a guanidine-based vulcanization accelerator. Here, in the coating rubber composition for an RFID tag of the present invention, the sulfur contains insoluble sulfur, and the content of the sulfur is 6.0 parts by mass or more with respect to 100 parts by mass of the rubber component.

[0018] General rubber compositions contain carbon black, but carbon black increases the relative permittivity of the rubber composition, shortens the communication distance (communicable distance) of RFID tags, and degrades communication performance. Here, if carbon black is not used, the crack resistance and elastic modulus of the rubber composition will decrease. On the other hand, the coating rubber composition for RFID tags of the present invention contains silica, and unlike carbon black, the silica does not increase the relative permittivity of the rubber composition, so the communication distance of the RFID tag can be lengthened and the communication performance can be improved. Further, by including silica, the crack resistance and elastic modulus of the rubber composition can be improved. However, if the rubber composition only contains silica instead of carbon black, the elastic modulus of the rubber composition will decrease and the vulcanization characteristics will deteriorate (the vulcanization rate will decrease). However, the coating rubber composition for RFID tags of the present invention can suppress the decrease in elastic modulus and the deterioration of vulcanization characteristics (the decrease in vulcanization rate) by including a guanidine-based vulcanization accelerator. Further, since the rubber composition has a sufficient elastic modulus, stress concentration on the RFID tag coated with the rubber composition can be suppressed, and adhesion between the rubber composition (coating rubber) and an adjacent rubber member can be ensured. Also, by setting the sulfur content to 6.0 parts by mass or more with respect to 100 parts by mass of the rubber component, the elastic modulus of the rubber composition can be improved. However, if general sulfur is blended at 2.5 parts by mass or more with respect to 100 parts by mass of the rubber component, the sulfur will bloom, the adhesiveness (tack) of the rubber composition will decrease, and the workability during tire molding of the rubber composition will decrease. On the other hand, in the coating rubber composition for RFID tags of the present invention, by including insoluble sulfur in the sulfur, blooming of the sulfur can be suppressed, a decrease in the adhesiveness of the rubber composition can be suppressed, and the workability during tire molding of the rubber composition can be improved. Therefore, the coating rubber composition for RFID tags of the present invention can sufficiently balance communication performance, crack resistance, adhesion to an adjacent rubber member, and elastic modulus, and is also excellent in workability.

[0019] (Rubber component) The coating rubber composition for RFID tags of the present invention contains a rubber component, and the rubber component provides rubber elasticity to the composition. As the rubber component, diene rubber is preferable, which may be natural rubber (NR), synthetic diene rubber, or may contain both. Examples of the synthetic diene rubber include isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene rubber (SIR), chloroprene rubber (CR), etc. The rubber component may be used alone or in a blend of two or more kinds.

[0020] (Sulfur) The coating rubber composition for RFID tags of the present invention contains sulfur. By containing sulfur in the rubber composition, it becomes vulcanizable, and the crack resistance and elastic modulus of the rubber composition are improved.

[0021] The content of the sulfur is 6.0 parts by mass or more with respect to 100 parts by mass of the rubber component. If the content of sulfur is less than 6.0 parts by mass with respect to 100 parts by mass of the rubber component, the elastic modulus of the rubber composition cannot be sufficiently improved, and the crack resistance decreases.

[0022] The content of the sulfur is preferably 6.5 parts by mass or more, and more preferably 6.8 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content of sulfur is 6.5 parts by mass or more with respect to 100 parts by mass of the rubber component, the crack resistance and elastic modulus of the rubber composition are further improved. Also, when the content of sulfur is 6.8 parts by mass or more with respect to 100 parts by mass of the rubber component, the crack resistance and elastic modulus of the rubber composition are further improved. Further, if the content of sulfur is less than 6.0 parts by mass with respect to 100 parts by mass of the rubber component, the elastic modulus decreases, and the durability of the tire may decrease.

[0023] The sulfur contains insoluble sulfur. By containing insoluble sulfur as sulfur, blooming of sulfur can be suppressed, reduction of the adhesiveness of the rubber composition can be suppressed, and the workability during tire molding can be improved. The aforementioned insoluble sulfur is sulfur that is insoluble in carbon disulfide (amorphous polymeric sulfur), and its solubility in rubber components is lower than that of soluble sulfur, making it less likely to cause blooming.

[0024] The proportion of insoluble sulfur in the sulfur is preferably 50% by mass or more, more preferably 80% by mass or more, and preferably 90% by mass or less. When the proportion of insoluble sulfur in the sulfur is 50% by mass or more, the effect of suppressing sulfur bloom is greatly enhanced, and the workability during tire molding can be further improved. If the proportion of insoluble sulfur in the sulfur is less than 50% by mass, sulfur bloom occurs when sulfur is added to maintain the elastic modulus, which reduces the workability during tire molding. When the proportion of insoluble sulfur in the sulfur is between 50% and 90% by mass, the effect of suppressing sulfur bloom is greatly enhanced, and the workability during tire molding can be further improved.

[0025] (silica) The RFID tag coating rubber composition of the present invention contains silica. By including silica in the rubber composition, the crack resistance and elastic modulus of the rubber composition can be improved without increasing the dielectric constant of the rubber composition. The dielectric constant of the rubber composition is preferably 4.0 or less, and more preferably 2.5 or less, from the viewpoint of the communication distance (communication range) of the RFID tag.

[0026] Examples of the silica include wet silica (hydrated silica), dry silica (anhydrous silica), calcium silicate, and aluminum silicate, with wet silica being preferred among these. These silicas may be used individually or in combination of two or more.

[0027] The silica content is preferably 40 parts by mass or more, preferably 100 parts by mass or less, and more preferably 60 to 80 parts by mass per 100 parts by mass of the rubber component. When the silica content 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. This is because if the silica content is less than 40 parts by mass per 100 parts by mass of the rubber component, the crack resistance decreases. When the silica content is 40 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.

[0028] (Guanidine-based vulcanization accelerator) The RFID tag coating rubber composition of the present invention contains a guanidine-based vulcanization accelerator. By including a guanidine-based vulcanization accelerator in the rubber composition, it is possible to suppress a decrease in elastic modulus and deterioration of vulcanization properties (decrease in vulcanization rate).

[0029] Examples of the guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. These guanidine-based vulcanization accelerators may be used individually or in combination of two or more.

[0030] As the guanidine-based vulcanization accelerator, 1,3-diphenylguanidine (DPG) is preferred. By including 1,3-diphenylguanidine (DPG) in the rubber composition, the vulcanization rate can be further improved, and the elastic modulus of the rubber composition can be further improved.

[0031] The content of the guanidine-based vulcanization accelerator is preferably 0.1 parts by mass or more, preferably 1.0 part by mass or less, and more preferably 0.3 to 0.7 parts by mass per 100 parts by mass of the rubber component. If the content of the guanidine-based vulcanization accelerator is 0.3 parts by mass or more per 100 parts by mass of the rubber component, the vulcanization rate can be further improved, and the elastic modulus of the rubber composition can be further improved. If the content of the guanidine-based vulcanization accelerator is less than 0.1 parts by mass per 100 parts by mass of the rubber component, the elastic modulus will decrease. When the content of the guanidine-based vulcanization accelerator is 0.1 to 1.0 parts by mass per 100 parts by mass of the rubber component, the vulcanization rate can be further improved, and the elastic modulus of the rubber composition can be further improved.

[0032] (others) The RFID tag coating rubber composition of the present invention preferably contains, in addition to the above-mentioned rubber components, sulfur, silica, and guanidine-based vulcanization accelerator, a silane coupling agent, oil, and a tackifier. Furthermore, the RFID tag coating rubber composition of the present invention may, if necessary, further contain various components commonly used in the rubber industry, such as fillers other than silica, antioxidants, waxes, softeners other than oils, processing aids, stearic acid, zinc oxide (zinc oxide), vulcanization accelerators other than guanidine-based vulcanization accelerators, and vulcanizing agents other than sulfur, selected as appropriate within a range that does not impair the purpose of the present invention. Commercially available products can be suitably used as these compounding agents.

[0033] When the rubber composition contains a silane coupling agent, the interaction between the rubber component and silica increases, improving the dispersibility of silica within the rubber component. Furthermore, improved dispersibility of silica within the rubber component allows the silica to exert its full effect, further improving the crack resistance and elastic modulus of the rubber composition. Examples of the silane coupling agents 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, and 3-triethoxysilylpropyl-N Examples include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide. From the viewpoint of further improving the dispersibility of silica in the rubber component and thereby further improving the crack resistance and elastic modulus of the rubber composition, the content of the silane coupling agent is preferably 5 to 20% by mass of the silica content (i.e., 5 to 20 parts by mass per 100 parts by mass of silica).

[0034] When the rubber composition contains oil, the cohesiveness of the rubber composition during mixing is improved, and the workability of the rubber composition during mixing is enhanced. The oil is a general term for the stretching oil contained in the rubber component and the liquid oil added as a compounding agent to the rubber composition, and includes petroleum-based softeners such as aromatic oils, paraffin-based oils, and naphthenic oils; and plant-based softeners such as palm oil, castor oil, cottonseed oil, and soybean oil. Among these, petroleum-based softeners such as aromatic oils, paraffin-based oils, and naphthenic oils are preferred.

[0035] As the oil, a naphthenic oil containing asphalt is preferred. When the rubber composition contains a naphthenic oil containing asphalt, the cohesiveness of the rubber composition during mixing is further improved, and the workability of the rubber composition during mixing is further enhanced. The naphthenic oil containing asphalt is preferably a mixture of naphthenic base oil and asphalt in a mass ratio of (95 / 5) to (30 / 70). Within this mass ratio range, the compatibility between the rubber component and the oil is further improved. As the naphthenic base oil, hydrogenated naphthenic base oil is preferred, and hydrogenated naphthenic base oil obtained by highly hydrogenating and refining aromatic oils or naphthenic oils using a high-pressure, high-temperature hydrogenation refining production apparatus is particularly preferred. Specifically, such hydrogenated naphthenic base oils are available commercially as SNH8, SNH46, SNH220, SNH440 (all trademarks) manufactured by Sankyo Yuka Kogyo Co., Ltd. Furthermore, considering compatibility with the rubber components used and the effect of improving cohesion during the mixing of the rubber composition, it is preferable that the asphalt mixed with the naphthenic base oil contains 5% by mass or less of asphalt. The asphalt is quantified by compositional analysis measured in accordance with the JPI method [Japan Petroleum Society standard JPI-5S-22-83 (established in 1983), standard name "Compositional analysis method of asphalt by column chromatography"]. Such asphalt is preferably straight asphalt, and particularly preferably naphthenic straight asphalt. Furthermore, the kinematic viscosity of the asphalt at 120°C is 300 mmHg. 2 It is preferable that it be less than or equal to / second. The method of mixing the asphalt is not particularly limited, but from the viewpoint of ease of preparation and economic efficiency, a method of preparing the asphalt by dissolving it in a naphthenic base oil (including spreader and compounding oils) is preferred. As the naphthenic oil containing asphalt, a preferred product is "A / O Mix," manufactured by Sankyo Yuka Kogyo Co., Ltd., which is obtained by mixing a hydrogenated naphthenic base oil produced by a high-pressure, high-temperature hydrogenation refining apparatus with naphthenic straight asphalt containing 5% or less asphalt by mass, in a mass ratio of 63 / 37. From the viewpoint of further improving the cohesiveness of the rubber composition during mixing and further improving workability during mixing, the oil content is preferably more than 0 parts by mass and 15 parts by mass or less per 100 parts by mass of the rubber component.

[0036] When the rubber composition contains a tackifier, the tackiness of the rubber composition is improved, and the workability of the rubber composition during tire molding is improved. Various natural resins and synthetic resins can be used as the tackifier, and specifically, it is preferable to use rosin-based resins, terpene-based resins, petroleum-based resins, phenol-based resins, coal-based resins, and xylene-based resins. These tackifiers may be used individually or in combination of two or more. When the rubber composition contains at least one 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 tackiness of the rubber composition is further improved, and the workability of the rubber composition during tire molding is further improved.

[0037] In the aforementioned natural resins, examples of rosin-based resins include gum rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, and modified rosin such as glycerin and pentaerythritol ester. Furthermore, examples of terpene resins in the aforementioned natural resins include terpene resins such as α-pinene, β-pinene, and dipentene resins, aromatically modified terpene resins, terpene phenol resins, and hydrogenated terpene resins. Among these natural resins, polymerized rosin, terpene phenol resin, and hydrogenated terpene resin are preferred from the viewpoint of the fracture resistance of the compounded rubber composition.

[0038] In the aforementioned synthetic resin, the petroleum-based resin is obtained, for example, by polymerizing a mixture of unsaturated hydrocarbons such as olefins and diolefins, which are produced as by-products along with basic petrochemical raw materials such as ethylene and propylene by the thermal decomposition of naphtha in the petrochemical industry, using a Friedel-Crafts type catalyst. Examples of the petroleum-based resin include aliphatic petroleum resins obtained by (co)polymerizing the C5 fraction obtained by the thermal decomposition of naphtha (hereinafter sometimes referred to as "C5 resins"), aromatic petroleum resins obtained by (co)polymerizing the C9 fraction obtained by the thermal decomposition of naphtha (hereinafter sometimes referred to as "C9 resins"), copolymerized petroleum resins obtained by copolymerizing the C5 fraction and the C9 fraction (hereinafter sometimes referred to as "C5-C9 resins"), alicyclic compound petroleum resins such as hydrogenated or dicyclopentadiene resins, and styrene resins such as styrene, substituted styrene, or copolymers of styrene and other monomers.

[0039] The C5 fraction obtained by the thermal decomposition of naphtha typically contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, as well as diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. Aromatic petroleum resins obtained by (co)polymerizing the C9 fraction are resins polymerized from C9 aromatic compounds, with vinyltoluene and indene as the main monomers. Specific examples of the C9 fraction obtained by the thermal decomposition of naphtha include styrene congeners such as α-methylstyrene, β-methylstyrene, and γ-methylstyrene, and indene congeners such as indene and coumarone. Trademarks include Petridine (Mitsui Petrochemical), Petrite (Mikuni Chemical), Neopolymer (Nippon Petrochemical), and Petol (Toyo Soda).

[0040] Furthermore, from the viewpoint of workability, a modified petroleum resin obtained by modifying the petroleum resin consisting of the C9 fraction can be suitably used. Examples of the modified petroleum resin include C9 petroleum resin modified with an unsaturated alicyclic compound, C9 petroleum resin modified with a compound having a hydroxyl group, and C9 petroleum resin modified with an unsaturated carboxylic acid compound.

[0041] Preferred unsaturated alicyclic compounds include cyclopentadiene and methylcyclopentadiene. Diels-Alder reaction products of alkylcyclopentadiene are also preferred as unsaturated alicyclic compounds, and examples of such products include dicyclopentadiene, cyclopentadiene / methylcyclopentadiene codimers, and tricyclopentadiene. Dicyclopentadiene is particularly preferred as the unsaturated alicyclic compound. Dicyclopentadiene-modified C9 petroleum resins can be obtained by thermal polymerization or the like in the presence of both dicyclopentadiene and a C9 fraction. An example of such dicyclopentadiene-modified C9 petroleum resin is Neopolymer 130S (manufactured by Nippon Petrochemical).

[0042] Furthermore, examples of compounds having hydroxyl groups include alcohol compounds and phenol compounds. Specific examples of alcohol compounds include, for example, alcohol compounds having double bonds such as allyl alcohol and 2-butene-1,4-diol. Phenolic compounds that can be used include alkylphenols such as phenol, cresol, xylenol, p-tert-butylphenol, p-octylphenol, and p-nonylphenol. These compounds having hydroxyl groups may be used individually or in combination of two or more. Furthermore, C9 petroleum resins having hydroxyl groups can be produced by methods such as thermal polymerization of (meth)acrylate alkyl esters, etc., together with a petroleum fraction to introduce ester groups into the petroleum resin, followed by reduction of the ester groups; or by retaining or introducing double bonds into the petroleum resin, followed by hydration of the double bonds. While C9 petroleum resins having hydroxyl groups can be obtained by the various methods described above, it is preferable to use phenol-modified petroleum resins from a performance and manufacturing standpoint. These phenol-modified petroleum resins are obtained by cationic polymerization of a C9 fraction in the presence of phenol, are easily modified, and are inexpensive. Examples of the phenol-modified C9 petroleum resin include Neopolymer E-130 (manufactured by Nippon Petrochemical Co., Ltd.).

[0043] Furthermore, the C9 petroleum resin modified with the aforementioned unsaturated carboxylic acid compound can be modified with an ethylenically unsaturated carboxylic acid. Typical examples of such ethylenically unsaturated carboxylic acids include (anhydride) maleic acid, fumaric acid, itaconic acid, tetrahydro(anhydride) phthalic acid, (meth)acrylic acid, or citraconic acid. The unsaturated carboxylic acid-modified C9 petroleum resin can be obtained by thermal polymerization of the C9 petroleum resin and the ethylenically unsaturated carboxylic acid. In the present invention, maleic acid-modified C9 petroleum resin is preferred. An example of an unsaturated carboxylic acid-modified C9 petroleum resin is Neopolymer 160 (manufactured by Nippon Petrochemical Co., Ltd.).

[0044] Furthermore, copolymer resins of C5 and C9 fractions obtained by the thermal decomposition of naphtha can be suitably used. There are no particular restrictions on the C9 fraction, but it is preferable that it be a C9 fraction obtained by the thermal decomposition of naphtha. Specifically, examples include TS30, TS30-DL, TS35, and TS35-DL from the Struktol series manufactured by Schill & Seilacher.

[0045] In the aforementioned synthetic resins, examples of phenolic resins include alkylphenol formaldehyde resins and their rosin-modified derivatives, alkylphenol acetylene resins, modified alkylphenol resins, terpene phenol resins, and more specifically, novolac-type alkylphenol resins such as Hitanol 1502 (manufactured by Hitachi Chemical Co., Ltd.) and p-tert-butylphenol acetylene resins such as Coresine (manufactured by BASF).

[0046] In the aforementioned synthetic resins, examples of coal-based resins include coumarone indene resin, and examples of xylene-based resins include xylene formaldehyde resin. In addition, polybutene can also be used as a resin that provides tackiness.

[0047] From the viewpoint of further improving the tackiness of the rubber composition and further improving workability during tire molding, the content of the tackifier is preferably more than 0 parts by mass and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0048] The RFID tag coating rubber composition of the present invention may or may not contain carbon black as a filler other than silica. Here, the carbon black content is preferably 20 parts by mass or less per 100 parts by mass of the rubber component, and it is particularly preferable that it be 0 parts by mass (i.e., no carbon black is included). When the carbon black content is 20 parts by mass or less per 100 parts by mass of the rubber component, the dielectric constant of the rubber composition decreases, and the communication distance of the RFID tag increases. Furthermore, when the carbon black content is 0 parts by mass (i.e., no carbon black is included), the dielectric constant of the rubber composition decreases further, and the communication distance of the RFID tag increases even further.

[0049] (Method for manufacturing rubber composition) The method for producing the rubber composition is not particularly limited, but for example, it can be produced by mixing the aforementioned rubber components, sulfur, silica, and guanidine-based vulcanization accelerator with various components as needed, and then kneading, heating, extruding, etc. Furthermore, the obtained rubber composition can be vulcanized to produce vulcanized rubber.

[0050] There are no particular restrictions on the mixing conditions, and various conditions such as the input volume of the mixing device, the rotation speed of the rotor, the ram pressure, as well as the mixing temperature, mixing time, and the type of mixing device can be appropriately selected according to the purpose. Examples of mixing devices include Banbury mixers, intermixes, kneaders, and rolls, which are commonly used for mixing rubber compositions.

[0051] There are no particular restrictions on the heat treatment conditions, and various conditions such as heat treatment temperature, heat treatment time, and heat treatment equipment can be appropriately selected according to the purpose. Examples of such heat treatment equipment include heat treatment roll machines commonly used for heat treatment of rubber compositions.

[0052] There are no particular restrictions on the extrusion conditions, and various conditions such as extrusion time, extrusion speed, extrusion equipment, and extrusion temperature can be appropriately selected according to the purpose. Examples of extrusion equipment include extruders typically used for extruding rubber compositions. The extrusion temperature can be determined as appropriate.

[0053] There are no particular restrictions on the apparatus, method, and conditions for performing the vulcanization, and they can be appropriately selected according to the purpose. Typical vulcanization apparatuses include molding vulcanizers using molds, which are commonly used for vulcanizing rubber compositions. The vulcanization temperature is typically around 100-190°C.

[0054] <Tires> The tire of the present invention is characterized by comprising an RFID tag coated with the above-described RFID tag coating rubber composition. Because the tire of the present invention comprises an RFID tag coated with the above-described RFID tag coating rubber composition, it has excellent communication performance, durability and productivity.

[0055] The aforementioned RFID tags are generally made of materials such as metal and resin. For example, in one embodiment, the RFID tag comprises an electronic device portion and an antenna portion connected to the electronic device portion, wherein the housing (or package) of the electronic device portion is made of resin and the antenna portion is made of metal. When coating the RFID tag with the RFID tag coating rubber composition of the present invention described above, sufficient adhesion between the RFID tag and the coating rubber can be ensured by applying an adhesive such as "ChemLock" (registered trademark) manufactured by Rhode Corporation to the RFID tag in advance.

[0056] Furthermore, since the RFID tag is harder than the rubber components in the tire, it is preferable that the coating rubber of the RFID tag has a higher modulus of elasticity (i.e., is harder) than adjacent rubber components (for example, the side rubber and stiffener described later) in order to suppress stress concentration on the RFID tag. The above-mentioned RFID tag coating rubber composition has a high modulus of elasticity and is hard, and therefore also has the effect of suppressing stress concentration on the RFID tag.

[0057] It is preferable to place the RFID tag in a part of the tire where there is relatively little distortion during driving. In one embodiment, it is preferable to place the RFID tag coated with the above-mentioned RFID tag coating rubber composition between a stiffener located on the radially outer side of the bead core embedded in the bead portion of the tire, and the side rubber located on the tire widthwise outer side of the carcass of the tire side. Furthermore, in this embodiment, it is even more preferable to place the RFID tag coated with the RFID tag coating rubber composition in a part located radially inward from the maximum width portion of the tire.

[0058] Figure 1 is a cross-sectional view of one embodiment of the tire of the present invention. The tire 1 shown in Figure 1 has a pair of bead portions 2 and a pair of side portions 3, and a tread portion 4 connected to both side portions 3, and comprises a carcass 5 that extends in a toroidal shape between the pair of bead portions 2 and reinforces these portions 2, 3, and 4, a belt 6 positioned on the radially outer side of the crown portion of the carcass 5, and stiffeners 8 positioned on the radially outer side of the ring-shaped bead cores 7 embedded in each of the bead portions 2. The stiffener 8 consists of a relatively rigid hard stiffener 8a adjacent to the radially outer side of the bead core 7, and a relatively rigid soft stiffener 8b adjacent to the radially outer side of the hard stiffener 8a. Furthermore, the side rubber 9 is positioned on the outer side in the tire width direction of the carcass 5 of the side section 3.

[0059] In the illustrated example tire 1, the carcass 5 has a main body portion 5a that extends toroidally between a pair of bead cores 7, and folded portions 5b that are wound radially outward from the inside to the outside 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. The stiffener 8 is positioned between the main body portion 5a of the carcass 5 and its folded portions 5b. A wire chafer 10 is also provided on the outer surface side of the folded portions 5b of the carcass 5, and the wire chafer 10 further extends along the outside in the tire width direction of the stiffener 8.

[0060] Furthermore, an RFID tag 12 covered with coating rubber 11 is positioned radially inward from the tire's widest point, between the side rubber 9 and the soft stiffener 8b, and on the radially outward side of the wire chafer 10. Here, the coating rubber 11 uses the RFID tag coating rubber composition described above. An RFID tag 12 (RFID tag-rubber composite) coated with coating rubber 11 can be manufactured, for example, by preparing two rubber sheets made of the above-mentioned RFID tag coating rubber composition and sandwiching the RFID tag 12 between the rubber sheets. The RFID tag-rubber composite can be laminated together with other rubber members to form a green tire, and the green tire can be vulcanized to produce the tire of this embodiment.

[0061] As described above, the rubber composition applied to the coated rubber 11 has good communication performance, so the tire 1 shown in Figure 1 has a long communication range and excellent communication performance. Furthermore, as described above, the rubber composition applied to the coating rubber 11 has a good balance of crack resistance, adhesion to adjacent rubber members, and elastic modulus, so the tire 1 shown in Figure 1 has excellent durability. Furthermore, as described above, the rubber composition applied to the coating rubber 11 has excellent workability, and therefore the tire 1 shown in Figure 1 has excellent productivity.

[0062] 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 undergone a pre-vulcanization process, and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and as the gas to fill the pneumatic tire, in addition to ordinary air or air with adjusted oxygen partial pressure, an inert gas such as nitrogen, argon, or helium can be used. [Examples]

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0064] <Preparation of rubber composition> Following the formulations shown in Table 1, the components excluding the vulcanization accelerator, vulcanizing agent, and other Pro chemicals were filled into a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to a filling ratio of 55% to 65%, and the mixture was kneaded at a rotation speed of 80 rpm until it reached 160°C or after 4 minutes. Then, the vulcanization accelerator, vulcanizing agent, and other Pro chemicals were added to the resulting mixture in the amounts shown in Table 1, and the mixture was kneaded at 80°C for 2 minutes using an open roll to obtain unvulcanized rubber compositions according to the formulations of each example and comparative example. Furthermore, sheet-shaped samples of crosslinked rubber compositions were produced by vulcanizing the unvulcanized rubber compositions at 145°C for 45 minutes.

[0065] <Evaluation of rubber compositions> The rubber compositions of the obtained examples and comparative examples were evaluated for communication performance, crack resistance, adhesion to adjacent rubber members, elastic modulus, and workability using the following methods. The results are shown in Table 1.

[0066] (1) Communication performance The relative permittivity of a vulcanized rubber composition is measured at 860 MHz using a relative permittivity meter on a plate sample. Previous measurements have shown that the relative permittivity can be estimated from the amount of carbon black in the rubber compound. Therefore, the relative permittivity is calculated.

[0067] (2) Crack resistance A vulcanized rubber test specimen was processed into a JIS No. 5 type specimen with a thickness of 2 mm, and a 0.5 mm crack was made in the center of the specimen. The test specimen was grasped at both ends, and repeated input was applied under the following conditions. The number of times until the test specimen fractured was measured. Test stress: 1.9 N·m Frequency: 5Hz Ambient temperature: 80℃ The table shows the number of cycles until breakage, rounded to the nearest hundred. The more times a test specimen is subjected to crack propagation, the better its crack propagation resistance. This means that the prototype tire made from the vulcanized rubber of the test specimen exhibits superior crack propagation resistance. If the number of times it is subjected to crack propagation exceeds 10,000, it can be said to have excellent crack propagation resistance.

[0068] (3) Durability evaluation (E') The dynamic modulus (E') was measured using a spectrometer (manufactured by Ueshima Seisakusho Co., Ltd.) under the conditions of a temperature of 24°C, a strain of 1%, and a frequency of 52Hz. A higher dynamic modulus (E') indicates that the rubber is harder and less prone to deformation, resulting in superior durability. This means that the tire made from the vulcanized rubber of the test specimen will have superior durability. Furthermore, vulcanized rubber with a high dynamic modulus (E') can suppress stress concentration on RFID tags and ensure adhesion to adjacent rubber components.

[0069] (4) Elastic modulus of vulcanized rubber (M100) The 100% modulus value (M100) of the vulcanized rubber test specimen was measured. The 100% modulus value (M100) was measured as the modulus tensile modulus (MPa) of a 2 mm thick vulcanized rubber test piece stretched to 100% at 25°C, based on JIS K 6251 (2017). A higher modulus of elasticity (M100) means that the material is less prone to deformation, resulting in superior durability. This means that the tire made from the vulcanized rubber of the test specimen will have superior durability. Furthermore, vulcanized rubber with a high modulus of elasticity (M100) can suppress stress concentration on RFID tags and ensure adhesion to adjacent rubber components.

[0070] (5) Workability Unvulcanized rubber was kneaded at 80°C for 2 minutes using an open roll to obtain a smooth rubber surface. The unvulcanized rubber sample was then stored in a constant temperature bath at 40°C for 2 weeks, and the presence or absence of bloom on the surface of the unvulcanized rubber was visually checked. Samples with blooming show a change in surface color to white, and there are concerns that the adhesion of the rubber will be greatly reduced, making tire molding difficult.

[0071] [Table 1]

[0072] *1 Natural rubber: RSS#3 *2 Silica: Manufactured by Tosoh Silica Co., Ltd., product name "NipSeal AQ" *3 Carbon Black (N330): Manufactured by Cabot, product name "VULCAN 3" *4 Silane coupling agent: Bis(3-triethoxylylpropyl) disulfide (average sulfur chain length: 2.35), silane coupling agent manufactured by Evonik, trade name "Si75" *5 Oil: Manufactured by Sankyo Yuka Kogyo Co., Ltd., product name "A / O Mix", naphthenic oil containing asphalt *6 Tackifier: SI Group RIBECOURT SAS, product name "R7510PJ" *7 Vulcanization accelerator DPG: 1,3-diphenylguanidine, manufactured by Sanshin Chemical Industry Co., Ltd., product name "Sunceller D" *8 Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazolyl sulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noxellar CZ-G" *9 Vulcanization accelerator TBzTD: Tetrabenzyl thiuram disulfide, manufactured by Sanshin Chemical Industry Co., Ltd., product name "Sunceller TBZTD" *10 Ordinary sulfur: Sulfur that does not contain insoluble sulfur, manufactured by Tsurumi Chemical Industries, Ltd., product name "Sulfax 5" *11 Insoluble sulfur: Sulfur containing insoluble sulfur, manufactured by Sanshin Chemical Industry Co., Ltd., product name "Sanfer Ex", percentage of insoluble sulfur in sulfur = 90% by mass

[0073] Table 1 shows that the rubber compositions of the embodiments according to the present invention can adequately balance communication performance, crack resistance, adhesion to adjacent rubber members, and elastic modulus, and also exhibit excellent workability. [Explanation of symbols]

[0074] 1: Tire, 2: Bead section, 3: Side section, 4: Tread section, 5: Carcass, 5a: Main body of the carcass, 5b: Folded-over section of the 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. It contains rubber components, sulfur, silica, and a guanidine-based vulcanization accelerator. The sulfur includes insoluble sulfur, A coating rubber composition for RFID tags, characterized in that the sulfur content is 6.0 parts by mass or more per 100 parts by mass of the rubber component.

2. The RFID tag coating rubber composition according to claim 1, wherein the silica content is 40 to 100 parts by mass per 100 parts by mass of the rubber component.

3. The RFID tag coating rubber composition according to claim 1, wherein the sulfur content is 6.8 parts by mass or more per 100 parts by mass of the rubber component.

4. The RFID tag coating rubber composition according to claim 1, wherein the content of the guanidine-based vulcanization accelerator is 0.1 to 1.0 part by mass per 100 parts by mass of the rubber component.

5. The RFID tag coating rubber composition according to claim 1, wherein the proportion of the insoluble sulfur in the sulfur is 50 to 90% by mass.

6. The RFID tag coating rubber composition according to claim 1, wherein the guanidine-based vulcanization accelerator is 1,3-diphenylguanidine (DPG).

7. A tire comprising an RFID tag coated with the RFID tag coating rubber composition described in Claim 1.

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