JP6356549B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire manufactured using a predetermined rubber composition.

The rubber composition used for the inner member of the tire is required to have a good balance of properties such as rubber breaking strength (destructive resistance), steering stability (rigidity), low fuel consumption, and electrical conductivity. ing.

As a method for improving the rubber breaking strength and rigidity, a method of increasing the amount of filler in the rubber composition is known. However, when the amount of the filler is increased, the fuel efficiency tends to be inferior. On the other hand, as a method for improving fuel economy, the use of a low reinforcing filler, the weight reduction of the filler, the use of silica, etc. are known. , Rigidity deteriorates. Thus, it is difficult to improve rubber breaking strength, rigidity, and low fuel consumption.

Furthermore, when silica is compounded in the tire rubber composition to satisfy the low fuel consumption, the electrical resistance of the tire increases, for example, a spark due to static electricity is generated when the vehicle is refueled, and the fuel is Risk of ignition. In particular, among the members for tires, it is necessary to dispose a member having a low electric resistance as an internal member such as a bead apex, a clinch apex, or an inner sidewall.

Thus, in the rubber composition for tires, a technique for improving electric conductivity, rubber breaking strength, low fuel consumption, and steering stability (rigidity) has been desired.

An object of the present invention is to solve the above-mentioned problems and to provide a pneumatic tire improved in electrical conductivity, rubber breaking strength, fuel efficiency and steering stability.

The present invention is a pneumatic tire produced using a rubber composition, wherein the rubber composition has a hydrogenation rate of a conjugated diene part obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound. The hydrogenated copolymer is 75 mol% or more, the content of the hydrogenated copolymer in 100% by mass of the rubber component is 75% by mass or more, and the volume resistivity of the rubber composition is 1.0. The present invention relates to a pneumatic tire that is 10 ¹⁰ Ω · cm or less.

The hydrogenated copolymer preferably has a weight average molecular weight of 200,000 to 2,000,000.

It is preferable that the hydrogenation rate of the hydrogenated copolymer is 90 mol% or more.

The hydrogenated copolymer is preferably a hydrogenated styrene butadiene copolymer.

The hydrogenated styrene butadiene copolymer preferably has a styrene content of 5 to 40% by mass.

The content of the hydrogenated styrene butadiene copolymer in 100% by mass of the rubber component is preferably 90 to 100% by mass.

The hydrogenated copolymer preferably has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 50 to 140.

The rubber composition preferably has a rubber hardness of 50 to 95.

The rubber composition further contains carbon black, and the content of carbon black with respect to 100 parts by mass of the rubber component is preferably 10 to 100 parts by mass.

The pneumatic tire of the present invention is preferably a pneumatic tire having at least one member selected from the group consisting of a bead apex, a clinch apex, and a conductive member produced using the rubber composition. .

According to the present invention, the specific hydrogenated copolymer having a hydrogenation rate of 75 mol% or more is contained in 75% by mass or more in 100% by mass of the rubber component, and the volume specific resistance of the rubber composition is 1.0 × 10 10. ^Since it is a pneumatic tire produced using a rubber composition of ¹⁰ Ω · cm or less, it has good electrical conductivity, rubber breaking strength, low fuel consumption, and steering stability.

The pneumatic tire of the present invention is a conjugated diene obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound (hereinafter also referred to as a copolymer of an aromatic vinyl compound and a conjugated diene compound). A hydrogenated copolymer having a hydrogenation ratio of 75 mol% or more is contained in 75 parts by mass or more in 100% by mass of the rubber component, and the volume resistivity is 1.0 × 10 ¹⁰ Ω · cm or less. It was produced using the rubber composition.

In the rubber composition of the present invention, the volume resistivity is 1.0 × 10 ¹⁰ Ω · cm or less, so that not only electric conductivity can be secured (static charge can be prevented) but also hydrogen in the conjugated diene part. By including a specific hydrogenated copolymer having an addition rate of 75 mol% or more in an amount of 75 mass% or more in 100 mass% of the rubber component, rubber breaking strength, fuel efficiency and steering stability can be improved satisfactorily. As a result, electrical conductivity, rubber breaking strength, low fuel consumption and steering stability (particularly rubber breaking strength) can be significantly improved.

The rubber composition in the present invention is characterized in that it contains a hydrogenated copolymer in which the conjugated diene portion of a copolymer of an aromatic vinyl compound and a conjugated diene compound is hydrogenated as a rubber component.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, and the like. These may be used singly or may be used in combination of two or more, but among them, the viewpoints of practical aspects such as the availability of monomers and the effect of the present invention can be more suitably obtained. To styrene is particularly preferred.

Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, and the like. These may be used singly or may be used in combination of two or more, but among them, the viewpoints of practical aspects such as the availability of monomers and the effect of the present invention can be more suitably obtained. 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred.

As a copolymer of an aromatic vinyl compound and a conjugated diene compound, a copolymer of styrene and 1,3-butadiene (styrene butadiene copolymer) is preferable. Accordingly, a hydrogenated styrene butadiene copolymer is preferred as the hydrogenated copolymer.

The styrene-butadiene copolymer is not particularly limited in the order of copolymerization as long as it is a copolymer of styrene and 1,3-butadiene, and may be random copolymer or block copolymer, but random copolymer is preferable. . The same applies to a copolymer of an aromatic vinyl compound and a conjugated diene compound other than the styrene-butadiene copolymer.

The hydrogenation rate of the hydrogenated copolymer (ratio of hydrogenation with respect to the conjugated diene part of the copolymer of aromatic vinyl compound and conjugated diene compound) is 75 mol% or more, preferably 80 mol% or more, More preferably, it is 90 mol% or more, More preferably, it is 93 mol% or more. When the hydrogenation rate is less than 75 mol%, it is difficult to improve fuel efficiency and handling stability. The hydrogenation rate of the hydrogenated copolymer is preferably 99 mol% or less, more preferably 98 mol% or less. If the hydrogenation rate exceeds 99 mol%, the rubber composition may become hard.
Note that the hydrogenation rate can be calculated from the spectral reduction rate of the unsaturated bonds of the spectrum obtained by measuring the H ¹ -NMR.

The weight average molecular weight (Mw) of the hydrogenated copolymer is preferably 200,000 or more, more preferably 400,000 or more. If Mw is less than 200,000, there is a possibility that good rubber breaking strength cannot be obtained. The Mw of the hydrogenated copolymer is preferably 2,000,000 or less, more preferably 1,000,000 or less, and still more preferably 700,000 or less. When Mw exceeds 2,000,000, the workability tends to decrease.

In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation), detector: differential refractometer, column: It can be determined by standard polystyrene conversion based on the measured value by TSKEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation.

When the hydrogenated copolymer is a hydrogenated styrene butadiene copolymer, the styrene content of the hydrogenated styrene butadiene copolymer is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass. % Or more, particularly preferably 20% by mass or more, and most preferably 25% by mass or more. If the styrene content is less than 5% by mass, sufficient grip performance may not be obtained. Further, the styrene content of the hydrogenated styrene butadiene copolymer is preferably 40% by mass or less, more preferably 35% by mass or less. When the styrene content exceeds 40% by mass, sufficient rubber breaking strength cannot be obtained, and the fuel efficiency may be deteriorated. When the styrene content is within the above range, the effect of the present invention can be more suitably obtained.
In addition, styrene content is measured by the method as described in the Example mentioned later.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the hydrogenated copolymer is preferably 50 or more, more preferably 70 or more, still more preferably 80 or more, because the effects of the present invention can be obtained more suitably. 140 or less, more preferably 120 or less, and still more preferably 100 or less.
The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the hydrogenated copolymer is measured by the method described in the examples below.

The hydrogenated copolymer preferably has a single tan δ (loss tangent) peak in the viscoelasticity measurement chart at −40 ° C. or higher and 30 ° C. or lower. When a plurality of tan δ peaks are present, the polymer constituent unit is blocked and a plurality of incompatible components are present in the polymer, and the fracture resistance tends to be lowered. Further, if the tan δ peak temperature is less than −40 ° C., the rigidity tends to be inferior, and if it exceeds 30 ° C., the fuel efficiency tends to be inferior. The tan δ peak temperature is more preferably −35 ° C. or higher, and further preferably −30 ° C. or higher. Further, the tan δ peak temperature is more preferably 20 ° C. or less, further preferably 10 ° C. or less, and particularly preferably 0 ° C. or less.

The tan δ peak temperature of the hydrogenated copolymer can be measured under the following conditions. That is, a test piece (vulcanized hydrogenated copolymer) having a predetermined size was prepared, and an initial strain of 10%, a dynamic strain of 0.5%, and a frequency of 10 Hz using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho Co., Ltd. And a temperature dispersion curve of tan δ at a temperature of −100 to 100 ° C. under the conditions of an amplitude of ± 0.25% and a heating rate of 2 ° C./min, and the temperature corresponding to the largest tan δ value in the temperature distribution curve is the tan δ peak Let it be temperature. The test piece can be obtained by press-vulcanizing an unvulcanized hydrogenated copolymer at 160 ° C. for 20 minutes to prepare a vulcanized sample.

The hydrogenated copolymer can be synthesized, for example, by subjecting a polymer obtained by polymerizing an aromatic vinyl compound and a conjugated diene compound to a hydrogenation treatment, and specifically, can be synthesized by the following method.

<Method for producing copolymer>
(Polymerization method)
There is no particular limitation on the polymerization method of the copolymer of the aromatic vinyl compound and the conjugated diene compound, and any of the solution polymerization method, the gas phase polymerization method, and the bulk polymerization method can be used, but the solution polymerization method is particularly preferable. Moreover, any of a batch type and a continuous type may be sufficient as the superposition | polymerization form.

When the solution polymerization method is used, the monomer concentration in the solvent (the total of styrene and 1,3-butadiene in the case of a styrene butadiene copolymer) is preferably 5% by mass or more, and more preferably 10% by mass or more. . When the monomer concentration in the solution is less than 5% by mass, the amount of the copolymer obtained is small and the cost tends to increase. The monomer concentration in the solvent is preferably 50% by mass or less, and more preferably 30% by mass or less. When the monomer concentration in the solvent exceeds 50% by mass, the solution viscosity becomes too high, stirring becomes difficult, and polymerization tends to be difficult.

(Polymerization initiator in anionic polymerization)
When anionic polymerization is performed, the polymerization initiator is not particularly limited, but an organic lithium compound is preferably used. As the organic lithium compound, those having an alkyl group having 2 to 20 carbon atoms are preferable. For example, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, tert- Octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butyl-phenyl lithium, 4-phenyl-butyl lithium, cyclohexyl lithium, cyclopentyl lithium, reaction products of diisopropenylbenzene and butyl lithium, etc. Among these, n-butyllithium or sec-butyllithium is preferable from the viewpoints of availability, safety, and the like.

(Method of anionic polymerization)
There is no restriction | limiting in particular as a method of manufacturing a copolymer by anionic polymerization using the said organolithium compound as a polymerization initiator, A conventionally well-known method can be used.
Specifically, in an organic solvent inert to the reaction, for example, a hydrocarbon solvent such as an aliphatic, alicyclic, or aromatic hydrocarbon compound, for example, butyl lithium is used as a polymerization initiator, and a randomizer is used as necessary. By subjecting styrene, 1,3-butadiene and the like to anionic polymerization in the presence of styrene, a desired copolymer such as a styrene-butadiene copolymer can be obtained.

(Hydrocarbon solvents in anionic polymerization)
The hydrocarbon solvent is preferably one having 3 to 8 carbon atoms, such as propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene and trans-2. -Butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene and the like. These may be used alone or in combination of two or more.

(Randomizer in anionic polymerization)
The randomizer is a microstructure control of a conjugated diene moiety in a copolymer, for example, an increase in 1,2-bond in butadiene, an increase in 3,4-bond in isoprene, or a composition of monomer units in the copolymer. It is a compound having an action of controlling distribution, for example, randomizing styrene units and butadiene units in a styrene-butadiene copolymer. The randomizer is not particularly limited, and any known compound generally used as a conventional randomizer can be used. For example, dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, bistetrahydrofurylpropane, triethylamine, pyridine, N-methylmorpholine, N, N, N ′, N′-tetramethylethylenediamine, 1,2-di Examples include ethers such as piperidinoethane and tertiary amines. Further, potassium salts such as potassium-t-amylate and potassium-t-butoxide, and sodium salts such as sodium-t-amylate can also be used. These randomizers may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of randomizer used is preferably 0.01 molar equivalents or more, more preferably 0.05 molar equivalents or more per mole of the organic lithium compound. If the amount of randomizer used is less than 0.01 molar equivalent, the effect of addition tends to be small and it tends to be difficult to randomize. The amount of randomizer used is preferably 1000 molar equivalents or less, more preferably 500 molar equivalents or less, per mole of the organic lithium compound. If the amount of randomizer used exceeds 1000 molar equivalents, the reaction rate of the monomer changes greatly, and conversely, it tends to be difficult to randomize.

(Reaction temperature)
The reaction temperature during the anionic polymerization is not particularly limited as long as the reaction proceeds suitably, but it is usually preferably −10 ° C. to 100 ° C., more preferably 25 ° C. to 70 ° C.

(Reaction stopped)
The anionic polymerization can be stopped by adding a reaction terminator usually used in this field. Examples of such a reaction terminator include polar solvents having active protons such as alcohols such as methanol, ethanol and isopropanol or acetic acid and mixtures thereof, or polar solvents and nonpolar solvents such as hexane and cyclohexane. A mixed solution is mentioned. The amount of the reaction terminator added is usually about the same molar amount or twice the molar amount relative to the anionic polymerization initiator.

(Coupling)
In the method for producing the copolymer, a coupling agent may be added to the hydrocarbon solution of the copolymer from the start of the polymerization of the monomer to the recovery of the polymer described later. Examples of the coupling agent include compounds represented by the following formula (1-1).
R ¹ _a ML _4-a (1-1)
(In formula (1-1), R ¹ represents an alkyl group, an alkenyl group, a cycloalkenyl group or an aryl group, M represents a silicon atom or a tin atom, L represents a halogen atom or a hydrocarbyloxy group, and a represents Represents an integer of 0 to 2.)

As the coupling agent represented by the above formula (1-1), silicon tetrachloride, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, tin tetrachloride, methyltrichlorotin, dimethyldichlorotin, trimethylchlorotin, tetramethoxy Examples include silane, methyltrimethoxysilane, dimethoxydimethylsilane, methyltriethoxysilane, ethyltrimethoxysilane, dimethoxydiethylsilane, diethoxydimethylsilane, tetraethoxysilane, ethyltriethoxysilane, and diethoxydiethylsilane.

The amount of the coupling agent added is preferably 0.03 mol or more, more preferably 0.05 mol or more, per 1 mol of alkali metal derived from the alkali metal catalyst in order to improve the processability of the polymer. Moreover, in order to improve low fuel consumption, Preferably it is 0.4 mol or less, More preferably, it is 0.3 mol or less.

(Hydrogen addition method)
In the method for producing a hydrogenated copolymer, the copolymer described so far is hydrogenated to obtain a hydrogenated copolymer having a hydrogenation rate of 75 mol% or more. There is an advantage that heat resistance is improved by hydrogenating the copolymer. Further, if the hydrogenation rate is low, the effect of improving fuel economy and steering stability cannot be obtained sufficiently.

There are no particular limitations on the hydrogenation method and reaction conditions, and hydrogenation may be performed using known methods and known conditions. Usually, it is carried out in the presence of a hydrogenation catalyst at 20 to 150 ° C. under hydrogen pressure of 0.1 to 10 MPa. The hydrogenation rate can be arbitrarily selected by changing the amount of the hydrogenation catalyst, the hydrogen pressure during the hydrogenation reaction, the reaction time, and the like. As the hydrogenation catalyst, a compound containing any of metals in Group 4 to 11 of the periodic table can be used. For example, a compound containing Ti, V, Co, Ni, Zr, Ru, Rh, Pd, Hf, Re, and Pt atoms can be used as the hydrogenation catalyst. More specific hydrogenation catalysts include metallocene compounds such as Ti, Zr, Hf, Co, Ni, Pd, Pt, Ru, Rh, and Re; metals such as Pd, Ni, Pt, Rh, and Ru are carbon, A supported heterogeneous catalyst supported on a carrier such as silica, alumina, diatomaceous earth; a homogeneous Ziegler catalyst in which an organic salt of a metal element such as Ni or Co or an acetylacetone salt and a reducing agent such as organoaluminum is combined; Examples include organometallic compounds or complexes such as Ru and Rh; fullerenes and carbon nanotubes in which hydrogen is occluded.

Of these, metallocene compounds containing any one of Ti, Zr, Hf, Co, and Ni are preferable in that they can be hydrogenated in a homogeneous system in an inert organic solvent. Furthermore, a metallocene compound containing any of Ti, Zr, and Hf is preferable. In particular, a hydrogenation catalyst obtained by reacting a titanocene compound with an alkyl lithium is preferable because it is an inexpensive and industrially useful catalyst. Specific examples include, for example, JP-A-1-275605, JP-A-5-271326, JP-A-5-271325, JP-A-5-222115, JP-A-11-292924, and JP-A-11-292924. JP 2000-37632 A, JP 59-133203 A, JP 63-5401 A, JP 62-218403 A, JP 7-90017 A, JP 43-19960 A, Mention may be made of the hydrogenation catalyst described in JP-B 47-40473. In addition, these hydrogenation catalysts can be used individually by 1 type or in combination of 2 or more types.

The content of the hydrogenated copolymer in 100% by mass of the rubber component is 75% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. is there. When the content of the hydrogenated copolymer is less than 75% by mass, it tends to be difficult to obtain an effect of improving the rubber breaking strength, fuel efficiency and steering stability (particularly rubber breaking strength).

In particular, when the hydrogenated copolymer is a hydrogenated styrene butadiene copolymer, the content of the hydrogenated styrene butadiene copolymer in 100% by mass of the rubber component is preferably 90% by mass or more, more preferably. Is 95% by mass or more, more preferably 100% by mass.

Other rubber components that can be used in addition to the hydrogenated copolymer include natural rubber (NR), epoxidized natural rubber (ENR), isoprene rubber (IR), butadiene rubber (BR), and conventional styrene butadiene rubber (SBR). ), Styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), thermoplastic elastomer (TPE) and the like. These may be modified and may be used alone or in combination of two or more. Among the above rubber components, SBR, SIBR, TPE having an aromatic vinyl component as a hard segment, and the like are preferable because of good compatibility with the hydrogenated copolymer.

The rubber composition in the present invention preferably further contains a filler. In the present specification, the filler is blended in a rubber composition for the purpose of reinforcing rubber, for example, mica such as silica, calcium carbonate, sericite, aluminum hydroxide, magnesium oxide, magnesium hydroxide, White fillers such as clay, talc, alumina, titanium oxide and mica; carbon black and the like. These fillers may be used in combination of two or more. The rubber composition in the present invention preferably contains carbon black as a filler, more preferably contains carbon black and white filler, and further preferably contains carbon black and silica. Thereby, the effect of this invention is acquired more suitably. In particular, by including carbon black, good electrical conductivity can be obtained.

When the rubber composition in the present invention contains carbon black, the carbon black may be a furnace black such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF and ECF. Acetylene black (acetylene carbon black); thermal black (thermal carbon black) such as FT and MT; channel black (channel carbon black) such as EPC, MPC and CC; graphite and the like. These can be used alone or in combination of two or more.

The rubber composition in the present invention may contain carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 400 m ² / g or more (hereinafter also referred to as high specific surface area carbon black) in order to improve electrical conductivity. . _N 2 SA of the high specific surface area carbon black is preferably at least 400 meters ² / g, more preferably at least 500 meters ² / g, more preferably not less than ^{700m 2 / g, 900m 2 /} g or more is particularly preferable. If it is less than 400 m < ² > / g, there exists a possibility that sufficient electroconductivity (prevention of accumulation of static electricity), low fuel consumption, rubber breaking strength, and steering stability cannot be improved. The _N 2 SA is preferably 2000 m ² / g or less, more preferably 1500 m ² / g, more preferably not more than 1350 m ² / g. If it exceeds 2000 m ² / g, it becomes difficult to disperse the high specific surface area carbon black, the fuel efficiency, rubber breaking strength, and steering stability deteriorate, and the electrical resistance of the tire over time tends to increase. is there. In addition, it is difficult to produce such carbon black, which may unnecessarily increase the cost.
Incidentally, _N 2 SA of carbon black, JIS K 6217-2: determined by 2001.

The rubber composition in the present invention may contain only the high specific surface area carbon black, or may further contain carbon black other than the high specific surface area carbon black. Further, the rubber composition in the present invention does not contain high specific surface area carbon black, and may contain only carbon black other than high specific surface area carbon black.

High specific surface area carbon carbon black nitrogen adsorption specific surface area of the non-black _(N 2 SA) of preferably from 300 meters ² / g or less, more preferably 200 meters ² / g, still more preferably 100 m ² / g or less, ^{80 m} 2 / Particularly preferred is g or less. If it exceeds 300 m ² / g, the fuel efficiency tends to deteriorate. The N ₂ SA is preferably 30 m ² / g or more, more preferably 35 m ² / g or more, and still more preferably 55 m ² / g or more. If it is less than 30 m ² / g, a sufficient reinforcing effect cannot be obtained, and sufficient rubber breaking strength and steering stability may not be obtained.

When the rubber composition in the present invention does not contain high specific surface area carbon black, the carbon black content is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably with respect to 100 parts by mass of the rubber component. Is 40 parts by mass or more, particularly preferably 50 parts by mass or more. If it is less than 10 parts by mass, the electrical conductivity, rubber breaking strength and steering stability tend to be inferior. The content is preferably 100 parts by mass or less, more preferably 90 parts by mass or less. When it exceeds 100 parts by mass, fuel economy, rubber breaking strength, and steering stability tend to deteriorate. Therefore, if it is within the above range, good electrical conductivity, rubber breaking strength, low fuel consumption and steering stability can be obtained.

When the rubber composition in the present invention contains a high specific surface area carbon black, the content of the high specific surface area carbon black is preferably based on 100 parts by mass of the rubber component because the effects of the present invention can be obtained more suitably. Is 0.1 parts by mass or more, more preferably 1 part by mass or more, further preferably 3 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 6 parts by mass or less. It is.

When the rubber composition in the present invention contains a high specific surface area carbon black, the total content of the high specific surface area carbon black and other carbon blacks is 100 masses of the rubber component because the effects of the present invention are more suitably obtained. Is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and preferably 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably. 60 parts by mass or less, particularly preferably 40 parts by mass or less. By using high specific surface area carbon black, even if the total content of carbon black in the rubber composition is reduced, the desired volume resistivity can be obtained, the weight of the tire can be reduced, and better fuel efficiency can be achieved. Sex is obtained.

As described above, the rubber composition in the present invention preferably contains a white filler, and more preferably contains silica. The silica is not particularly limited, and examples thereof include dry method silica (anhydrous silica), wet method silica (hydrous silica) and the like, and wet method silica is preferable because of its large number of silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² / g or more, more preferably 50 m ² / g or more, still more preferably 100 m ² / g or more, and particularly preferably 150 m ² / g or more. If it is less than 40 m ² / g, rubber breaking strength, fuel efficiency and steering stability may be deteriorated. Further, N ₂ SA of silica is preferably 300 m ² / g or less, more preferably 250 m ² / g or less, and further preferably 200 m ² / g or less. When it exceeds 300 m ² / g, it is difficult to disperse silica, and there is a risk that fuel efficiency and processability will deteriorate.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

When the rubber composition in the present invention contains silica, the content of silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 13 parts by mass or more with respect to 100 parts by mass of the rubber component. is there. The silica content is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and still more preferably 30 parts by mass or less. If it exceeds 40 parts by mass, fuel efficiency may be deteriorated. The effect of this invention is acquired more suitably as content of a silica exists in the said range.

The rubber composition in the present invention preferably uses a silane coupling agent in combination with silica. In the present invention, since the hydrogenated copolymer having a high hydrogenation rate is used, a sufficient crosslinking density may not be obtained. However, silica and a silane coupling agent are blended together with the hydrogenated copolymer. As a result, a good crosslinked network can be formed, and the effects of the present invention can be obtained more suitably.

As the silane coupling agent, conventionally known silane coupling agents can be used, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxy). Silylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) ) Disulfide, bis (3-trimethoxysilylpropyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-trie Sulfide systems such as xylsilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2- Mercapto series such as mercaptoethyltrimethoxysilane and 2-mercaptoethyltriethoxysilane, vinyl series such as vinyltriethoxysilane and vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane and other amino-based, γ-glycidoxypropyltrie Glycidoxy systems such as toxisilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 3-nitropropyltrimethoxysilane, 3-nitropropyltri Examples thereof include nitro series such as ethoxysilane, and chloro series such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane. In addition, said silane coupling agent may be used independently and may be used in combination of 2 or more type. Of these, sulfide-based silane coupling agents are preferred from the viewpoint of the coupling effect, processability, and cost of the silane coupling agent, such as bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl). Disulfide is more preferred.

The content of the silane coupling agent is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and further preferably 2.5 parts by mass or more with respect to 100 parts by mass of silica. When the amount is less than 0.5 parts by mass, high silica dispersion tends to be not obtained. Further, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 13 parts by mass or less with respect to 100 parts by mass of silica. Even if it exceeds 20 parts by mass, the effect of improving the dispersion of silica is difficult to obtain, and the cost tends to increase unnecessarily. In addition, the scorch time is shortened, and the workability during kneading and extrusion tends to decrease.

When the rubber composition does not contain high specific surface area carbon black, the total content of carbon black and white filler (preferably silica) other than the high specific surface area carbon black is preferably 100 parts by mass of the rubber component. It is 40 parts by mass or more, more preferably 60 parts by mass or more, and still more preferably 70 parts by mass or more. The total content is preferably 100 parts by mass or less, more preferably 95 parts by mass or less, and still more preferably 90 parts by mass or less. Within the above range, good rubber breaking strength, electrical conductivity, low fuel consumption and steering stability can be obtained.

When the rubber composition contains a high specific surface area carbon black, the total content of the high specific surface area carbon black, the other carbon black and the white filler (preferably silica) is preferably 100 parts by mass of the rubber component. 20 mass parts or more, More preferably, it is 30 mass parts or more, More preferably, it is 40 mass parts or more. The total content is preferably 80 parts by mass or less, more preferably 65 parts by mass or less, and still more preferably 50 parts by mass or less. Within the above range, good rubber breaking strength, electrical conductivity, low fuel consumption and steering stability can be obtained. In particular, by blending high specific surface area carbon black, good electrical conductivity can be obtained with a small amount of carbon black, so the amount of filler used can be reduced to the above amount, and the weight of the tire can be reduced. Low fuel consumption can be obtained.

In addition to the above components, the rubber composition in the present invention includes a vulcanizing agent such as sulfur; a thiazole vulcanization accelerator, a thiuram vulcanization accelerator, a sulfenamide vulcanization accelerator, and a guanidine vulcanization accelerator. Vulcanization accelerators such as agents; vulcanization activators such as stearic acid and zinc oxide; organic peroxides; processing aids such as extenders (oils) and lubricants; Can be used.

As the extending oil (oil), aromatic mineral oil (viscosity specific gravity constant (VGC value) 0.900 to 1.049), naphthenic mineral oil (VGC value 0. 850 to 0.899), paraffinic mineral oil (VGC value 0.790 to 0.849), and the like. The polycyclic aromatic content of the extender oil is preferably less than 3% by mass, more preferably less than 1% by mass. The polycyclic aromatic content is measured according to the British Petroleum Institute 346/92 method. Moreover, the aromatic compound content (CA) of the extending oil is preferably 20% by mass or more. These extending oils may be used in combination of two or more.

Examples of the vulcanization accelerator include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and thiazole vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram monosulfide, tetramethylthiuram disulfide Thiuram vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N- Sulfenamide vulcanization accelerators such as oxyethylene-2-benzothiazole sulfenamide, N, N′-diisopropyl-2-benzothiazole sulfenamide; diphenylguanidine, diortolylguanidine, orthotolylbiguanidine, etc. Guani It can be mentioned emission-based vulcanization accelerator. Of these, sulfenamide-based vulcanization accelerators are preferable and N-cyclohexyl-2-benzothiazole sulfenamide is more preferable because the effects of the present invention can be more suitably obtained. It is also preferable to use a guanidine vulcanization accelerator in combination. 0.1-5 mass parts is preferable with respect to 100 mass parts of rubber components, and, as for the usage-amount of a vulcanization accelerator, More preferably, it is 0.2-4 mass parts.

Although it does not specifically limit as a vulcanizing agent, Sulfur can be used conveniently. The content of sulfur is preferably 0.5 to 5 parts by mass, more preferably 1 to 3 parts by mass with respect to 100 parts by mass of the rubber component. Thereby, the effect of this invention is acquired more suitably.

The rubber composition in the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The rubber composition (vulcanized rubber composition) in the present invention is characterized by having a volume resistivity of 1.0 × 10 ¹⁰ Ω · cm or less. Thereby, the outstanding electrical conductivity (antistatic effect) is obtained. The volume resistivity is preferably 1.0 × 10 ⁹ Ω · cm or less, more preferably 1.0 × 10 ⁸ Ω · cm or less, still more preferably 1.0 × 10 ⁷ Ω · cm or less, particularly preferably 1 0.0 × 10 ^6.5 Ω · cm or less, most preferably 1.0 × 10 ⁶ Ω · cm or less, preferably 1.0 × 10 ³ Ω · cm or more, more preferably 1.0 × 10 ⁴ Ω · cm or more. If the volume resistivity is within the above range, the effect of the present invention can be obtained more suitably.
In addition, volume specific resistance is measured by the method as described in the Example mentioned later. Hereinafter, in the present invention, when the volume resistivity is simply described, it means the volume resistivity measured at 10V.

By adjusting the type of filler and the compounding ratio of the rubber composition, the volume specific resistance of the rubber composition can be adjusted. For example, the volume resistivity of the rubber composition can be reduced by increasing the amount of carbon black.

The rubber composition (vulcanized rubber composition) in the present invention preferably has a rubber hardness of 50 to 95.
When the rubber composition in the present invention is used as a bead apex and / or a clinch apex, the rubber hardness of the rubber composition is preferably 50 or more, more preferably 55 or more, still more preferably 60 or more, particularly Preferably it is 70 or more. If it is less than 50, the steering stability may deteriorate. The rubber hardness is preferably 95 or less, more preferably 93 or less, and still more preferably 90 or less. If it exceeds 95, peeling from other rubber members may occur, or rubber strength may be reduced.
Further, when the rubber composition in the present invention is used as a conductive member inside a tread or a sidewall such as an under tread or an inner sidewall, the rubber hardness of the rubber composition is preferably 50 or more, more preferably 52 or more. is there. The rubber hardness is preferably 95 or less, more preferably 65 or less, and still more preferably 60 or less. Within the above range, the difference in hardness from other members is small, and the steering stability and rubber breaking strength are excellent.
In addition, rubber hardness is measured by the method as described in the Example mentioned later.

The rubber composition in the present invention can be used for each member of a tire (tread, sidewall, carcass, belt, bead apex, clinch apex, conductive member, etc.), among others, bead apex, clinch apex and conductive It is suitably used as at least one member selected from the group consisting of members.

The bead apex is a rubber portion disposed inside the tire clinch so as to extend outward from the bead core in the radial direction, and specifically, FIGS. This is the member shown in FIG.

The clinch apex is a rubber portion disposed on the inner end of the sidewall. Specifically, for example, FIG. 1 of Japanese Patent Application Laid-Open No. 2008-75066, FIG. It is a member shown by these.

The conductive member is a member such as an inner layer sidewall (inner sidewall) or an under tread. The inner side wall is an inner layer portion of the side wall having a multilayer structure, and specifically, is a member shown in FIG. 1 of Japanese Patent Application Laid-Open No. 2007-106166. The under tread is a member that is located between the tread rubber and the breaker (belt) rubber and covers the tire surface side portion of the breaker rubber. Specifically, the figure of JP 2009-191132 A It is a member shown in 1 etc.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing a hydrogenated copolymer and, if necessary, a rubber composition containing the above-mentioned various compounding agents, each tire member such as a bead apex, a clinch apex, a conductive member, etc. at an unvulcanized stage. An unvulcanized tire is formed by extruding in accordance with the shape and molding it together with other tire members by a normal method on a tire molding machine. The pneumatic tire of the present invention is obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

The pneumatic tire of the present invention is preferably used as a tire for passenger cars, a tire for trucks and buses, a tire for motorcycles, a tire for competition, and the like, and particularly preferably used as a tire for passenger cars.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used at the time of synthesis and polymerization will be described together. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
THF: anhydrous tetrahydrofuran n-hexane manufactured by Kanto Chemical Co., Inc .: styrene manufactured by Kanto Chemical Co., Ltd. butadiene manufactured by Kanto Chemical Co., Ltd .: 1,3-butadiene n-butyllithium solution manufactured by Tokyo Chemical Industry Co., Ltd .: 1.6M n-butyllithium hexane solution 2,6-di-tert-butyl-p-cresol manufactured by Kanto Chemical Co., Inc .: NOCRACK 200 manufactured by Ouchi Shinsei Chemical Co., Ltd.
Alcohol: Methanol manufactured by Tokyo Chemical Industry Co., Ltd.

Moreover, the evaluation method of the obtained copolymer is demonstrated collectively below.

(Measurement of hydrogenation rate of conjugated diene part of copolymer)
A solution having a concentration of 15% by mass was prepared using carbon tetrachloride as a solvent, and calculated from the spectrum reduction rate of the unsaturated bond part of 100 MHz H ¹ -NMR.

(Measurement of styrene content)
H ¹ -NMR was measured at 25 ° C. using a JEOL JNM-A 400 NMR apparatus, and phenyl protons based on 6.5 to 7.2 ppm styrene units and 4.9 to 5.4 ppm butadiene were obtained from the spectrum. The styrene content was determined from the ratio of vinyl protons based on units.

(Measurement of weight average molecular weight (Mw), number average molecular weight (Mn))
The weight average molecular weight (Mw) and number average molecular weight (Mn) of the copolymer were determined by gel permeation chromatography (GPC) (GPC-8000 series, manufactured by Tosoh Corporation), detector: differential refractometer, column: Tosoh Corporation ) Obtained from TSKGEL SUPERMULTIPORE HZ-M, manufactured by TSKGEL, based on standard polystyrene conversion.

(Mooney viscosity (ML _{1 + 4} , 100 ° C.))
According to JIS K 6300: 2001-1, using a Mooney viscometer (SMV-200) manufactured by Shimadzu Corporation, preheated at 100 ° C. for 1 minute, then measured for 4 minutes to determine the Mooney viscosity of the copolymer ( ML _{1 + 4} , 100 ° C.).

<Example of copolymer production>
Synthesis Example 1 (Synthesis of copolymer (1): hydrogenation rate 0 mol%)
In a heat-resistant reaction vessel sufficiently purged with nitrogen, add 2000 ml of n-hexane, 60 g of styrene, 140 g of 1,3-butadiene, 1.75 g of THF, and 0.45 mmol of n-butyllithium, and stir at 50 ° C. for 5 hours to conduct the polymerization reaction. went. Thereafter, alcohol was added to stop the reaction, and 1 g of 2,6-di-tert-butyl-p-cresol was added to the reaction solution, and then copolymer (1) was obtained by reprecipitation purification. The obtained copolymer (1) had a weight average molecular weight (Mw) of 490,000 and a styrene content of 30% by mass.

Synthesis Example 2 (Synthesis of copolymer (2): hydrogenation rate 60 mol%)
A copolymer (2) was obtained by the same formulation as the copolymer (1) except that the obtained polymer was hydrogenated. That is, after the polymerization conversion reaction in the copolymer (1), alcohol is not added to stop the polymerization reaction, and then the mixture is stirred for 20 minutes while supplying hydrogen gas at a pressure of 0.4 MPa-Gauge. Reaction with terminal lithium gave lithium hydride. Hydrogenation was performed using a catalyst mainly composed of titanocene dichloride at a hydrogen gas supply pressure of 0.7 MPa-Gauge, a reaction temperature of 90 ° C. When the amount of hydrogen absorption reaches an integrated amount that achieves the target hydrogenation rate, the reaction temperature is brought to room temperature, the hydrogen pressure is returned to normal pressure, the reaction vessel is withdrawn from the reaction vessel, the reaction solution is stirred into water, and the solvent is steamed. By removing by stripping, a hydrogenated copolymer was obtained. The resulting copolymer (2) had a hydrogenation rate of 60 mol% and a weight average molecular weight (Mw) of 450,000.

Synthesis Example 3 (Synthesis of copolymer (3): hydrogenation rate 80 mol%)
A copolymer (3) was obtained by the same formulation as the copolymer (2) except that the cumulative amount of hydrogen suction was adjusted so as to achieve the target hydrogenation rate. The resulting copolymer (3) had a hydrogenation rate of 80 mol% and a weight average molecular weight (Mw) of 480,000.

Synthesis Example 4 (Synthesis of copolymer (4): hydrogenation rate 95 mol%)
A copolymer (4) was obtained by the same formulation as the copolymer (2) except that the integrated amount of hydrogen suction was adjusted so as to achieve the target hydrogenation rate. The resulting copolymer (4) had a hydrogenation rate of 95 mol% and a weight average molecular weight (Mw) of 450,000.

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
Natural rubber: TSR20
Copolymers (1) to (4): Synthetic carbon black by the above method (1): Show Black N330 (N ₂ SA: 75 m ² / g) manufactured by Cabot Japan Co., Ltd.
Carbon black (2): PRINTEX XE2B manufactured by Degussa (N ₂ SA: 1000 m ² / g, DBP: 420 ml / 100 g)
Silica: ULTRASIL VN3 manufactured by EVONIK (N ₂ SA: 180 m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Oil: VivaTec400 (TDAE oil) manufactured by H & R Co., Ltd.
Anti-aging agent: Antigen 3C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Beads manufactured by NOF Corporation Zinc stearate Zinc oxide: Zinc flower No. 1 manufactured by Mitsui Kinzoku Mining Co., Ltd. Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. (1): Soxinol CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Sumitomo Chemical Co., Ltd.
Vulcanization accelerator (2): Soxinol D (1,3-diphenylguanidine) manufactured by Sumitomo Chemical Co., Ltd.

(Examples and Comparative Examples)
According to the composition shown in Table 2 and Table 3, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at 150 ° C. using a 1.7 L Banbury mixer manufactured by Kobe Steel Co., Ltd. A kneaded product was obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 0.5 mm thick mold at 170 ° C. for 20 minutes to obtain a vulcanized rubber composition.
The resulting unvulcanized rubber composition (compounded in Table 2) is formed into a bead apex and clinch apex shape and bonded together with other tire members on a tire molding machine to form an unvulcanized tire. And vulcanized at 170 ° C. for 12 minutes to produce a test tire (size: 195 / 65R15). Further, the obtained unvulcanized rubber composition (compound of Table 3) is molded into the shape of an under tread and an inner sidewall, and bonded together with other tire members on a tire molding machine to form an unvulcanized tire. And vulcanized at 170 ° C. for 12 minutes to produce a test tire (size: 195 / 65R15).

<Evaluation items and test methods>
The following evaluation was performed about the obtained vulcanized rubber composition and the tire for a test. The results are shown in Tables 2 and 3.

(Volume resistivity)
Using the above vulcanized rubber composition, a test piece having a thickness of 2 mm and a size of 15 cm × 15 cm was prepared, and vulcanized using an electric resistance measurement R8340A manufactured by ADVANTEST under conditions of a voltage of 10 V, an air temperature of 23 ° C., and a humidity of 55% The volume specific resistance (Ω · cm) of the rubber composition was measured. The common logarithm of the result is shown in Table 2 and Table 3. The larger the value, the higher the volume resistivity of the rubber composition and the poorer electrical conductivity.

(Rubber breaking strength)
The vulcanized rubber composition was subjected to a tensile test according to JIS K 6251 and measured for elongation at break. The measurement results are shown as an index with Comparative Example 1-1 or 2-1 as 100. The larger the index, the greater the rubber breaking strength.
(Rubber breaking strength index) = (Rubber breaking strength of each compound) / (Rubber breaking strength of Comparative Example 1-1 or 2-1) × 100

(Low fuel consumption)
Using a spectrometer manufactured by Ueshima Seisakusho, tan δ of the vulcanized rubber composition was measured at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50 ° C. The reciprocal value of tan δ was indicated as an index with Comparative Example 1-1 or 2-1 as 100. Larger values indicate lower rolling resistance and better fuel efficiency.

(Maneuvering stability)
The test tires were mounted on all wheels of a vehicle (domestic FF2000cc) and the vehicle was run on the test course, and the driving stability was evaluated by sensory evaluation of the driver. At that time, the steering stability of each of the test tires was evaluated relative to the steering stability of Comparative Example 1-1 or 2-1 as 100. The larger the value, the better the steering stability.

(Rubber hardness)
The rubber hardness of the vulcanized rubber composition was measured with a type A durometer according to JIS K 6253 “Method for testing hardness of vulcanized rubber and thermoplastic rubber”. The larger the value, the higher the rubber hardness and the better the steering stability.

From Tables 2 and 3, the hydrogenated styrene butadiene copolymer having a hydrogenation rate of 75 mol% or more is contained in 75% by mass or more in 100% by mass of the rubber component, and the volume specific resistance of the rubber composition is 1.0. In Examples 1-1 to 1-3, 2-1 and 2-2 using a rubber composition of × 10 ¹⁰ Ω · cm or less, electrical conductivity, rubber breaking strength, low fuel consumption, and steering stability are obtained. It became clear that it can be remarkably improved.

Furthermore, from Table 3, in Examples 2-1 and 2-2, in addition to carbon black (1), N ₂ SA contains high specific surface area carbon black (carbon black (2)) with 1000 m ² / g. It was revealed that even when the black content was reduced, the same performance as in Examples 1-1 to 1-3 using only carbon black (1) was obtained.

The rubber composition of Table 2 of the present application can be suitably used for the bead apex and clinch apex, and the rubber composition of Table 3 of the present application can be suitably used for the conductive member.

Claims (9)

A pneumatic tire produced using a rubber composition,
The rubber composition includes a hydrogenated copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene compound, wherein a hydrogenation rate of the conjugated diene part is 75 mol% or more,
The content of the hydrogenated copolymer in 100% by mass of the rubber component is 75% by mass or more,
Ri volume resistivity of 1.0 × ^{10 10} Ω · cm der less of the rubber composition,
A pneumatic tire , wherein the rubber composition has a rubber hardness of 50 to 95 . The pneumatic tire according to claim 1, wherein the hydrogenated copolymer has a weight average molecular weight of 200,000 to 2,000,000. The pneumatic tire according to claim 1 or 2, wherein a hydrogenation rate of the hydrogenated copolymer is 90 mol% or more. The pneumatic tire according to any one of claims 1 to 3, wherein the hydrogenated copolymer is a hydrogenated styrene butadiene copolymer. The pneumatic tire according to claim 4, wherein the hydrogenated styrene-butadiene copolymer has a styrene content of 5 to 40% by mass. The pneumatic tire according to claim 4 or 5, wherein a content of the hydrogenated styrene-butadiene copolymer in 100% by mass of the rubber component is 90 to 100% by mass. The pneumatic tire according to any one of claims 1 to 6, wherein the hydrogenated copolymer has a Mooney viscosity (ML _{1 + 4} , 100 ° C) of 50 to 140. The rubber composition further includes carbon black,
The pneumatic tire according to any one of claims 1 to 7 , wherein the carbon black content is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component. A bead apex made using the rubber composition, according to any one of claims 1 to 8 which is a pneumatic tire having at least one member selected from the group consisting of clinch apex and the conductive member Pneumatic tire.