JP2012101751A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relieve a fall of the inner pressure in a tire and the crack growth of the inner liner by the repeated flexion deformity with the tire running and to relieve the rolling resistance furthermore, in the pneumatic tire equipped with the inner liner.SOLUTION: In the pneumatic tire in which the inside of the carcass ply tire loaded across a pair of bead parts includes the inner liner, the inner liner consists of the first layer arranged inside the tire and the second layer arranged so as to come in contact with the rubber layer of the carcass ply. At least either of the first layer and the second layer is an isobutylene based block copolymer which consists of the polymeric block (A) made mainly of the isobutylene and a polymeric block (B) made mainly of the aromatic vinyl based compound, and at least one block is an elastomer composition containing the isobutylene based modified copolymer of a random copolymer containing β-pinene.

Description

  The present invention relates to a pneumatic tire provided with an inner liner, and more particularly to a pneumatic tire that prevents peeling of the inner liner due to repeated bending deformation during tire travel, reduces a decrease in tire internal pressure, and further reduces rolling resistance.

  In recent years, tires have been made lighter due to the strong social demand for lower fuel consumption of vehicles, and the amount of air leakage from the inside of a pneumatic tire to the outside (located inside the tire among tire members) ( There is also a strong demand for weight reduction in an inner liner having a function of improving air permeation resistance by reducing air pressure drop.

  At present, the rubber composition for an inner liner improves the air permeation resistance of a tire by using a rubber compound mainly composed of butyl rubber including, for example, 70 to 100% by mass of butyl rubber and 30 to 0% by mass of natural rubber. Has been done. Further, the rubber blend mainly composed of butyl rubber contains about 1% by mass of isoprene in addition to butylene, and this, together with sulfur, vulcanization accelerator, and zinc white, enables crosslinking between rubber molecules. The butyl rubber usually requires a thickness of about 0.6 to 1.0 mm for passenger car tires and about 1.0 to 2.0 mm for truck and bus tires. Therefore, there is a demand for a polymer that has better air permeation resistance than butyl rubber and that can reduce the thickness of the inner liner layer.

  Conventionally, in order to reduce the weight of a tire, a film made of a material containing a thermoplastic resin instead of the rubber composition has been proposed. However, if a tire is manufactured using a thin inner liner made of a thermoplastic resin, the pressure in the vulcanization process is partially reduced so that the finished gauge of the inner liner of the tire product becomes thinner than the design. In addition to the impression that the carcass cord is raised at that location (open thread), the inner liner with a thin finish will give the user an impression that the appearance is poor, and if the inner liner is thin, the gas barrier property will be partially degraded As a result, the tire internal pressure decreases, and in the worst case, the tire may burst.

  The inner liner is subjected to a large shear strain in the vicinity of the shoulder when the tire is running. When a material containing a thermoplastic resin is used as the inner liner, there is a problem that due to this shear strain, peeling is likely to occur at the adhesive interface between the inner liner and the carcass ply, resulting in tire air leakage.

  In order to reduce the weight of the inner liner, a technique using a thermoplastic elastomer material has also been proposed. However, a material that is thinner than the inner liner of butyl rubber and has high air permeability is inferior in vulcanization adhesion to the insulation rubber and carcass ply rubber adjacent to the inner liner than the inner liner of butyl rubber. I know.

  When the vulcanization adhesive strength of the inner liner is low, air is mixed between the inner liner and the insulation rubber or the carcass rubber, and a so-called air-in phenomenon occurs in which a small balloon appears. Many small spots on the inside of the tire give the user an impression that the appearance is poor, and air is the starting point during driving, causing separation and cracking in the inner liner, resulting in a decrease in tire internal pressure. In such a case, the tire may burst.

  In Patent Document 1, it is proposed to improve adhesion by using petroleum resin or terpene resin as a tackifier for SIBS, which is a thermoplastic elastomer. However, in addition to SIBS, a polyamide-based polymer is blended, and there is a problem that bending crack resistance is lowered.

  Patent Document 2 describes the adhesion of carcass ply rubber using a natural rosin, terpene, chroman indene resin, petroleum resin or alkylphenol resin as a tackifier to a blend of SIBS and sulfur crosslinkable polymer. It has been proposed to improve.

  However, in the technology of blending 10 to 300 parts by weight of a polymer capable of sulfur vulcanization with respect to 100 parts by weight of SIBS, when the sulfur crosslinkable polymer is 100 parts by weight or less, SIBS is a matrix (sea part), The sulfur-crosslinkable polymer has a domain structure (island portion), and the adhesive force at the contact interface with the carcass rubber is not improved. In addition, when the sulfur crosslinkable polymer is 100 parts by weight or more, gas barrier properties are reduced except for butyl rubber, adhesive strength is reduced with butyl rubber, and depending on the polymer to be blended, the adhesion becomes high and the thickness is 600 μm or less. There is a problem that a film cannot be produced.

JP 2010-13646 A JP 2010-1000067 A

  The present invention provides a pneumatic tire including an inner liner that reduces a decrease in the internal pressure of the tire, reduces crack growth of the inner liner due to repeated bending deformation accompanying tire running, and further reduces rolling resistance. The purpose is to do.

  The present invention is a pneumatic tire provided with an inner liner inside a tire of a carcass ply mounted between a pair of bead portions, wherein the inner liner includes a first layer disposed inside the tire, It is comprised by the 2nd layer arrange | positioned so that the rubber | gum layer of a carcass ply may be contacted, and at least any one of the said 1st layer and 2nd layer is a polymer block (A) which has isobutylene as a main component, and aromatic An isobutylene block copolymer comprising a polymer block (B) mainly composed of a vinyl compound, wherein at least one block is a random copolymer containing β-pinene. The present invention relates to the pneumatic tire which is an elastomer composition.

  The elastomer composition of the first layer preferably contains 10% by mass or more and 100% by mass or less of the isobutylene-based modified copolymer in the elastomer component. Moreover, it is preferable that the elastomer composition of said 2nd layer is 5 to 80 mass% of isobutylene type modified copolymers in an elastomer component.

  Further, the isobutylene-based modified copolymer has a β-pinene content of 0.5 to 25% by weight, the isobutylene-based modified copolymer has a weight average molecular weight Mw of 30,000 to 300,000, and a molecular weight. The distribution value (weight average molecular weight Mw / number average molecular weight Mn) is preferably 1.3 or less.

  The isobutylene-based modified copolymer contains styrene-isobutylene-styrene block copolymer, styrene-isoprene-styrene block copolymer, or styrene block of styrene-isobutylene block copolymer containing β-pinene. Is preferred.

  In the present invention, the inner liner is composed of a composite layer of a first layer disposed inside the tire and a second layer disposed in contact with the carcass ply, and isoprene-based modified copolymer is used for at least one of them. Therefore, the vulcanization adhesion between the first layer and the second layer can be improved. As a result, the adhesion between the first layer / carcass ply, the first layer / second interlayer, and the carcass ply / second layer is improved, and the tire durability is improved.

It is a schematic sectional drawing of the right half of the pneumatic tire of this invention. FIG. 2A to FIG. 2D are schematic sectional views showing the arrangement of the inner liner and the carcass.

<Tire structure>
In the present invention, a pneumatic tire having an inner liner on the inner side of the tire will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the right half of a pneumatic tire. In the figure, a pneumatic tire 1 has a tread portion 2 and sidewall portions 3 and bead portions 4 so as to form a toroid shape from both ends of the tread portion. Further, a bead core 5 is embedded in the bead portion 4. In addition, a carcass ply 6 provided from one bead portion 4 to the other bead portion, with both ends wound around the bead core 5 and locked, and at least two sheets on the outer side of the crown portion of the carcass ply 6 A belt layer 7 made of a ply is arranged.

  The belt layer 7 usually intersects two plies made of steel cords or cords such as aramid fibers with respect to the tire circumferential direction so that the cords are usually at an angle of 5 to 30 °. Are arranged as follows. In addition, a topping rubber layer can be provided on both outer sides of the belt layer to reduce peeling at both ends of the belt layer. In the carcass ply, organic fiber cords such as polyester, nylon, and aramid are arranged at approximately 90 ° in the tire circumferential direction. In the region surrounded by the carcass ply and the folded portion, the bead core 5 extends from the upper end to the sidewall direction. An extending bead apex 8 is arranged. Further, an inner liner 9 extending from one bead portion 4 to the other bead portion 4 is disposed inside the carcass ply 6 in the tire radial direction.

<Inner liner>
In the present invention, the inner liner is composed of a first layer disposed inside the tire and a second layer disposed so as to contact the rubber layer of the carcass ply. At least one of the first layer and second layer elastomer compositions contains an isobutylene-based modified copolymer.

<Isobutylene-modified copolymer>
In the present invention, the isobutylene-based modified copolymer is an isobutylene-based modified copolymer comprising a polymer block (A) mainly composed of isobutylene and a polymer block (B) mainly composed of an aromatic vinyl compound. And at least one block is a random copolymer containing β-pinene.

  The polymer block (A) containing isobutylene as a main component is a polymer block composed of 80% by weight or more of units whose soft segments are derived from isobutylene. Such a polymer block can be produced using aliphatic olefins, dienes, vinyl ethers, silanes, vinyl carbazole, acenaphthylene and the like as monomer components.

  On the other hand, the polymer block (B) mainly composed of an aromatic vinyl compound is a polymer block composed of 80% by weight or more of units whose hard segments are derived from an aromatic vinyl compound.

  Examples of aromatic vinyl compounds include styrene, methyl styrene, α-methyl styrene, β-methyl styrene, 2,6-dimethyl styrene, 2,4-dimethyl styrene, α-methyl-o-methyl styrene, α-methyl- m-methylstyrene, α-methyl-p-methylstyrene, β-methyl-o-methylstyrene, β-methyl-m-methylstyrene, β-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, α-methyl-2,6-dimethylstyrene, α-methyl-2,4-dimethylstyrene, β-methyl-2,6-dimethylstyrene, β-methyl-2,4-dimethylstyrene, chlorostyrene, 2,6 -Dichlorostyrene, 2,4-dichlorostyrene, α-chloro-o-chlorostyrene, α-chloro-m-chlorostyrene, α-chloro-p-chloro Styrene, β-chloro-o-chlorostyrene, β-chloro-m-chlorostyrene, β-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, α-chloro-2,6-dichlorostyrene, α -Chloro-2,4-dichlorostyrene, β-chloro-2,6-dichlorostyrene, β-chloro-2,4-dichlorostyrene, t-butylstyrene, methoxystyrene, chloromethylstyrene, bromomethylstyrene, etc. Is done. Styrene and α-methylstyrene are particularly preferable from the viewpoint of cost.

  The isobutylene-based modified copolymer of the present invention is a random copolymer in which at least one of the polymer blocks (A) and (B) is β-pinene. From the viewpoint of low temperature characteristics, it is preferable to copolymerize with a polymer block (B) mainly composed of an aromatic vinyl compound.

  On the other hand, from the viewpoint of adhesiveness, it is preferably copolymerized with the polymer block (A) mainly composed of isobutylene. In this case, the content of β-pinene is preferably 0.5 to 25% by weight, more preferably 2 to 25% by weight of the isobutylene-based modified copolymer. When the content of β-pinene is less than 0.5% by weight, the adhesiveness is not sufficient, and when it exceeds 25% by weight, it becomes brittle and rubber elasticity tends to be lowered.

  The structure of the isobutylene-based modified copolymer of the present invention is not particularly limited, and includes a block copolymer, a triblock copolymer, a multiblock copolymer having a linear, branched, or star-like molecular chain structure. Either of these can be selected. From the viewpoint of physical property balance and molding processability, the polymer blocks (A) and (B) are diblock copolymers ((A)-(B)) and triblock copolymers ((B)-(A)- The structure of (B)) can be adopted. These may be used alone or in combination of two or more in order to obtain desired physical properties and moldability.

  The molecular weight of the isobutylene-based modified copolymer is preferably 30,000 to 300,000 in terms of weight average molecular weight by GPC measurement from the viewpoints of fluidity, molding processability, rubber elasticity, and the like. Is particularly preferred. When the weight average molecular weight is lower than 30,000, mechanical properties tend not to be sufficiently exhibited, whereas when it exceeds 300,000, fluidity and workability tend to deteriorate. Furthermore, from the viewpoint of processing stability, the molecular weight distribution value (weight average molecular weight / number average molecular weight) of the isobutylene-based modified copolymer is preferably 1.3 or less.

<Method for producing isobutylene-based modified copolymer>
A method for producing an isobutylene-based modified copolymer is disclosed in, for example, Japanese Patent Application Laid-Open No. 2010-195969. For example, it can be produced by polymerizing the monomer component in the presence of a polymerization initiator represented by the following general formula (I).

(CR ¹ R ² X) nR ³ (1)
Wherein X is a halogen atom, a substituent selected from an alkoxy group having 1 to 6 carbon atoms or an acyloxy group, R ¹ and R ² are each a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, R ¹ , R ² may be the same or different, R ³ is a monovalent or polyvalent aromatic hydrocarbon group or a monovalent or polyvalent aliphatic hydrocarbon group, and n represents a natural number of 1 to 6. .)
The compound represented by the general formula (1) serves as an initiator, generates a carbon cation in the presence of a Lewis acid or the like, and serves as a starting point for cationic polymerization. Examples of the compound of the general formula (1) include bis (1-chloro-1-methylethyl) benzene [C ₆ H ₄ (C (CH ₃ ) ₂ Cl) ₂ ], tris (1-chloro-1-methyl). Ethyl) benzene [(ClC (CH ₃ ) ₂ ) ₃ C ₆ H ₃ ].

When producing an isobutylene-based modified copolymer, a Lewis acid catalyst can be allowed to coexist. The Lewis acid can be used for cationic polymerization. For example, metal halides such as TiCl ₄ , TiBr ₄ , BCl ₃ , BF ₃ , BF ₃ .OEt ₂ , ZnBr ₂ , AlCl ₃ ; Et ₂ AlCl, EtAlCl _2, etc. These organometallic halides can be used. The Lewis acid can be used in an amount of 0.1 to 100 molar equivalents relative to the compound represented by the general formula (1).

  In the production of the isobutylene-based modified copolymer, an electron donor component can be allowed to coexist. Examples of the electron donor component include pyridines, amines, amides, and sulfoxides.

  Polymerization of the isobutylene-based modified copolymer can be performed in an organic solvent, and an organic solvent that does not inhibit cationic polymerization can be used. For example, halogenated hydrocarbons such as methyl chloride, dichloromethane, chloroform, ethyl chloride, dichloroethane, alkylbenzenes such as benzene, toluene, xylene, ethylbenzene, and linear aliphatic carbonization such as ethane, propane, butane, pentane, hexane, heptane, etc. Hydrogen, branched aliphatic hydrocarbons such as 2-methylpropane and 2-methylbutane, and cyclic aliphatic hydrocarbons such as cyclohexane, methylcyclohexane and ethylcyclohexane can be used.

  The amount of the organic solvent is adjusted so that the concentration of the copolymer is 5 to 40% by mass from the viewpoint of viscosity adjustment and heat dissipation of the copolymer solution to be produced. The copolymerization reaction is preferably in the range of -20 ° C to -70 ° C.

<First layer>
In the present invention, the elastomer component of the elastomer composition used for the first layer of the inner liner is composed of an isoprene-based modified copolymer alone or a mixture with other elastomer components.

  The isoprene-based modified copolymer is in the range of 10 to 100% by mass, preferably 30 to 100% by mass of the entire elastomer component. When the isoprene-based modified copolymer is less than 10% by mass, the vulcanization adhesive strength with the second layer may be reduced.

  As the elastomer component, a thermoplastic elastomer, particularly a styrene thermoplastic elastomer is preferably used. Here, the styrene thermoplastic elastomer refers to a copolymer containing a styrene block as a hard segment. For example, styrene-isoprene-styrene block copolymer (hereinafter also referred to as “SIS”), styrene-isobutylene block copolymer (hereinafter also referred to as “SIB”), styrene-butadiene-styrene block copolymer ( Hereinafter, also referred to as “SBS”), styrene-isobutylene-styrene block copolymer (hereinafter also referred to as “SIBS”), styrene-ethylene-butene-styrene block copolymer (hereinafter also referred to as “SEBS”). ), Styrene-ethylene / propylene-styrene block copolymer (hereinafter also referred to as “SEPS”), styrene-ethylene / ethylene / propylene / styrene block copolymer (hereinafter also referred to as “SEEPS”), styrene-. Butadiene / butylene-styrene block copolymer (hereinafter referred to as “SBB”) Also referred to as ".) There is.

  The styrenic thermoplastic elastomer may have an epoxy group in its molecular structure. For example, Epofriend A1020 manufactured by Daicel Chemical Industries, Ltd. (weight average molecular weight is 100,000, epoxy equivalent is 500). An epoxy-modified styrene-butadiene-styrene copolymer (epoxidized SBS) can be used. Of the styrene-based thermoplastic elastomers, a styrene-isobutylene-styrene block copolymer is preferably used.

  A rubber component can be mixed as an elastomer component of the first layer. By mixing the rubber component, it is possible to impart adhesiveness to an adjacent carcass ply in an unvulcanized state, and to improve vulcanization adhesion to the carcass ply and insulation by vulcanization.

  The rubber component preferably contains at least one selected from the group consisting of natural rubber, isoprene rubber, chloroprene rubber and butyl rubber. The compounding amount of the rubber component is preferably in the range of 5 to 20% by mass with respect to 100 parts by mass of the thermoplastic epolymer component.

  The thickness of the first layer is 0.05 to 0.6 mm. When the thickness of the first layer is less than 0.05 mm, the first layer is broken by pressing pressure during vulcanization of a green tire in which the polymer laminate is applied to the inner liner, and an air leak phenomenon occurs in the obtained tire. May occur. On the other hand, if the thickness of the first layer exceeds 0.6 mm, the tire weight increases and the fuel efficiency performance decreases. The thickness of the first layer is preferably 0.05 to 0.4 mm. The first layer can be obtained by forming SIBS into a film by an ordinary method of forming a thermoplastic resin or thermoplastic elastomer into a film such as extrusion molding or calendar molding.

<Second layer>
In the present invention, the elastomer component of the elastomer composition used for the second layer of the inner liner is composed of a mixture of an isoprene-modified copolymer and another elastomer component.

  The isoprene-based modified copolymer is in the range of 5 to 80% by mass, preferably 10 to 60% by mass, based on the entire elastomer component. If the isoprene-modified copolymer is less than 5% by mass, the vulcanization adhesion with the first layer may be reduced, and if it exceeds 80% by mass, the vulcanization adhesion with the carcass ply may be reduced. There is sex.

  As the elastomer component of the elastomer composition used for the second layer, a thermoplastic elastomer, particularly a styrene thermoplastic elastomer is preferably used. Examples of styrenic thermoplastic elastomers include styrene-isoprene-styrene block copolymer (SIS), styrene-isobutylene block copolymer (SIB), styrene-butadiene-styrene block copolymer (SBS), and styrene-isobutylene-styrene. Block copolymer (SIBS), styrene-ethylene-butene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer There are a combination (SEEPS) and a styrene-butadiene-butylene-styrene block copolymer (SBBS).

  In particular, a thermoplastic elastomer composition containing at least one of styrene-isoprene-styrene block copolymer (SIS) and styrene-isobutylene block copolymer (SIB) is preferable.

  Of the styrenic thermoplastic elastomers used in the second layer, SIS and SIB are particularly suitable. Since the isoprene block of the styrene-isoprene-styrene copolymer (SIS) is a soft segment, the polymer film made of SIS is easily vulcanized and bonded to the rubber component. Therefore, when a polymer film made of SIS is used for the inner liner, the inner liner is excellent in adhesiveness with, for example, the rubber layer of the carcass ply, so that a pneumatic tire excellent in durability can be obtained.

  From the viewpoint of rubber elasticity and moldability, the molecular weight of the SIS is preferably 100,000 to 290,000 in terms of weight average molecular weight as measured by GPC. If the weight average molecular weight is less than 100,000, the tensile strength may be lowered, and if it exceeds 290,000, the extrusion processability is deteriorated. The content of the styrene component in the SIS is preferably 10 to 30% by mass from the viewpoints of tackiness, adhesiveness, and rubber elasticity.

  In the present invention, the polymerization degree of each block in SIS is preferably about 500 to 5,000 for isoprene and about 50 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

  The SIS can be obtained by a general vinyl compound polymerization method, for example, a living cationic polymerization method. The SIS layer can be obtained by forming the SIS into a film by a usual method of forming a thermoplastic resin or a thermoplastic elastomer into a film such as extrusion molding or calendar molding.

  Since the isobutylene block of the styrene-isobutylene block copolymer (SIB) is a soft segment, the polymer film made of SIB is easily vulcanized and bonded to the rubber component. Therefore, when a polymer film made of SIB is used as an inner liner, the inner liner is excellent in adhesiveness with an adjacent rubber forming a carcass or an insulation, for example, so that a pneumatic tire excellent in durability is obtained. be able to.

  It is preferable to use a linear SIB from the viewpoint of rubber elasticity and adhesiveness. The molecular weight of SIB is not particularly limited, but from the viewpoint of rubber elasticity and moldability, the weight average molecular weight by GPC measurement is preferably 40,000 to 120,000. If the weight average molecular weight is less than 40,000, the tensile strength may be lowered, and if it exceeds 120,000, the extrusion processability may be deteriorated.

  The content of the styrene component in the SIB is preferably 10 to 35% by mass from the viewpoints of tackiness, adhesiveness, and rubber elasticity. In the present invention, the polymerization degree of each block in SIB is preferably about 300 to 3,000 for isobutylene and about 10 to 1,500 for styrene from the viewpoint of rubber elasticity and handling.

  The SIB can be obtained by a living polymerization method of a general vinyl compound. For example, methylcyclohexane, n-butyl chloride, and cumyl chloride are added to a stirrer, cooled to -70 ° C, and reacted for 2 hours. Then, a production method is disclosed in which a large amount of methanol is added to stop the reaction and vacuum drying is performed at 60 ° C. to obtain SIB.

  The SIB layer can be formed by a usual method of forming SIB into a film of a styrenic thermoplastic elastomer such as extrusion molding or calendar molding.

  The thickness of the second layer is preferably 0.01 mm to 0.3 mm. Here, the thickness of the second layer refers to the thickness when the second layer is composed of only one layer such as a SIS layer or SIB. On the other hand, when the second layer is a two-layer or third layer including, for example, a SIS layer and an SIB layer, it means the total thickness of these. If the thickness of the second layer is less than 0.01 mm, the second layer may be broken by the press pressure during vulcanization of the raw tire in which the polymer laminate is applied to the inner liner, and the vulcanization adhesive force may be reduced. There is. On the other hand, if the thickness of the second layer exceeds 0.3 mm, the tire weight may increase and the fuel efficiency performance may deteriorate. The thickness of the second layer is further preferably 0.05 to 0.2 mm.

  The second layer can be composed of a composite layer of the SIS layer and the SIB layer, but the third layer is further provided between the first layer and the SIS layer, between the first layer and the SIB layer, or between the SIS layer and the SIB layer. As described above, a film made of urethane rubber or silicone rubber can be disposed.

  The styrenic thermoplastic elastomer may have an epoxy group in its molecular structure. For example, Epofriend A1020 manufactured by Daicel Chemical Industries, Ltd. (weight average molecular weight is 100,000, epoxy equivalent is 500). An epoxy-modified styrene-butadiene-styrene copolymer (epoxidized SBS) can also be used.

<SIBS mixture>
The second layer can be composed of a mixture of SIS and SIBS, or a mixture of SIB and SIBS. In this case, the amount of SIBS is adjusted in the range of 10 to 80% by mass, preferably 30 to 70% by mass of the elastomer component. When the SIBS is less than 10% by mass, the adhesion with the first layer is lowered, and when the SIBS exceeds 80% by mass, the adhesion with the carcass ply tends to be lowered.

<Tackifier>
In this invention, 0.1-100 mass parts of tackifiers are mix | blended with respect to 100 mass parts of elastomer components at least any one of the said 1st layer and 2nd layer. Here, the tackifier refers to a compounding agent for increasing the tackiness of the elastomer composition, and examples thereof include the following tackifiers.

  Typically, there are C9 petroleum resin and C5 petroleum resin. Here, C9 petroleum resin is obtained by thermally decomposing naphtha to obtain useful compounds such as ethylene, propylene, butadiene, etc., but the remaining C5-C9 fraction (mainly C9 fraction) from which they have been removed is mixed. It is an aromatic petroleum resin obtained by polymerization as it is. For example, as trade names, Alcon P70, P90, P100, P125, P140, M90, M100, M115, M135 (all manufactured by Arakawa Chemical Industries, Ltd., softening point 70 to 145 ° C.), and I-MABE S100, S110 , P100, P125, P140 (all manufactured by Idemitsu Petrochemical Co., Ltd., aromatic copolymer hydrogenated petroleum resin, softening point 100-140 ° C., weight average molecular weight 700-900, bromine number 2.0-6.0 g) / 100 g) and Petcoal XL (manufactured by Tosoh Corporation).

  C5 petroleum resin is obtained by thermally decomposing naphtha to obtain useful compounds such as ethylene, propylene and butadiene. The remaining C4 to C5 fractions (mainly C5 fractions) from which they have been removed are mixed. It is an aliphatic petroleum resin obtained by polymerization as it is. Product names include Highletz G100 (Mitsui Petrochemical Co., Ltd., softening point 100 ° C.), Marcarez T100AS (Maruzen Oil Co., Ltd., softening point 100 ° C.), and Escorez 1102 (Tonex Corp., softening) The point is 110 ° C.).

  Terpene resins are, for example, YS Resin PX800N, PX1000, PX1150, PX1250, PXN1150N, Clearon P85, P105, P115, P125, P135, P150, M105, M115, K100 (all manufactured by Yasuhara Chemical Co., Ltd.) The point is 75 to 160 ° C.).

  Examples of the aromatic modified terpene resin include YS resin TO85, TO105, TO115, and TO125 (all manufactured by Yashara Chemical Co., Ltd., softening point: 75 to 165 ° C.).

  The terpene phenol resins are, for example, trade names such as TAMANOL 803L, 901 (Arakawa Chemical Industries, softening point 120 ° C. to 160 ° C.), and YS polystar U115, U130, T80, T100, T115, T145, T160 (any Also from Yashara Chemical Co., Ltd., softening point 75-165 ° C).

  Coumarone resin includes, for example, coumarone resin having a softening point of 90 ° C. (manufactured by Kobe Oil Chemical Co., Ltd.). Coumaron indene oil has, for example, 15E (manufactured by Kobe Oil Chemical Co., Ltd., pour point 15 ° C.) as a trade name.

  For example, rosin ester has a trade name of ester gum AAL, A, AAV, 105, AT, H, HP, HD (all manufactured by Arakawa Chemical Industries, Ltd., softening point 68 ° C to 110 ° C), and Harrier Star TF. , S, C, DS70L, DS90, DS130 (all manufactured by Harima Kasei Co., Ltd., softening point 68 ° C to 138 ° C).

  Examples of the hydrogenated rosin ester include super esters A75, A100, A115, and A125 (all manufactured by Arakawa Chemical Industries, Ltd., softening point: 70 ° C to 130 ° C). The alkylphenol resin includes, for example, TAMANOL 510 (manufactured by Arakawa Chemical Industries, Ltd., softening point: 75 ° C to 95 ° C) as a trade name. DCPD has a trade name of Escorez 5300 (manufactured by Tonex Co., Ltd., softening point 105 ° C.).

  As for the tackifier, the fully hydrogenated petroleum resin of C9 petroleum resin has good compatibility with SIB, and can improve the adhesion without deteriorating the gas barrier property. It also has the effect of lowering the viscosity and can be advantageously used for film extrusion.

  The tackifier is blended in the range of 0.1 to 100 parts by mass, preferably 1 to 50 parts by mass with respect to 100 parts by mass of the thermoplastic elastomer of the first layer. When the tackifier is less than 0.1 parts by mass, the vulcanization adhesive strength with the second layer is not sufficient, while when it exceeds 100 parts by mass, the tackiness becomes too high, and the workability and productivity are reduced. The gas barrier property is further lowered.

  The second layer is disposed between the first layer inside the tire and the carcass ply, and adhesion between them is required. Then, the said tackifier is mix | blended in 0.1-100 mass parts with respect to 100 mass parts of thermoplastic elastomer of a 2nd layer, Preferably, it is 1-50 mass parts. When the tackifier is less than 0.1 parts by mass, the vulcanization adhesive strength with the first layer is not sufficient. On the other hand, when it exceeds 100 parts by mass, the tackiness becomes too high, and the workability and productivity are reduced. The gas barrier property is further lowered.

<Additive of elastomer composition>
A crosslinking agent and a crosslinking aid can be added to the elastomer composition of the first layer and the second layer. As the crosslinking agent, sulfur, tetramethylthiuram disulfide, 4,4-dithiobismorpholine, organic peroxide, phenol formaldehyde resin, and halomethylphenol can be used.

  Examples of crosslinking aids include metal oxides such as sulfenamide, benzothiazole, guanidine, dithiocarbamic acid and zinc oxide, fatty acids such as stearic acid, nitrogen-containing compounds, triallyl isocyanurate, ethylene glycol dimethacrylate, and trimethylolpropane methacrylate. Can be used. The compounding quantity of a crosslinking agent and a crosslinking adjuvant is 0.3-6 mass parts with respect to 100 mass parts of elastomer components.

  The elastomer composition may further contain a filler, an anti-aging agent, a softening agent, a processing aid and the like. As the filler, carbon black, wet silica, dry silica, calcium carbonate, kaolin, talc, clay and the like can be used. Anti-aging agents include antioxidants, UV absorbers, and light stabilizers. As the softening agent, paraffinic oil, naphthenic oil, aroma oil, rapeseed oil, dioctyl phthalate and the like can be used. Further, higher fatty acids, fatty acid esters, fatty acid metal salts, fatty acid amides, paraffin waxes, fatty alcohols, fluorine / silicone resins and the like can be used as processing aids.

<Polymer laminate>
In the present invention, the inner liner is a polymer laminate composed of a first layer and a second layer. Here, the first layer and the second layer are preferably thermoplastic elastomer compositions, and are in a softened state in a mold at a vulcanization temperature, for example, 150 ° C. to 180 ° C. The softened state means an intermediate state between solid and liquid with improved molecular mobility. Further, when the thermoplastic elastomer composition is in a softened state, the reactivity is improved as compared with the solid state, and therefore, the thermoplastic elastomer composition adheres and adheres to an adjacent member. Therefore, in order to prevent the shape change of the thermoplastic elastomer, the adhesion with the adjacent member, and the fusion, a cooling step is required when manufacturing the tire. A cooling process cools the inside of a bladder part rapidly for 10 to 300 seconds after tire vulcanization to 50-120 ° C. As the cooling medium, at least one selected from air, water vapor, water and oil is used. By adopting such a cooling step, it is possible to form a thin inner liner having an inner liner in the range of 0.05 to 0.6 mm.

  Next, the arrangement state with the carcass ply in the vulcanized tire of the inner liner will be specifically shown based on FIG. In FIG. 2 (a), the polymer laminate PL is composed of a first layer PL1 and a SIS main layer PL2 as a second layer. When the polymer laminate PL is applied to the inner liner of a pneumatic tire, if the SIS main layer PL2 is installed outward in the tire radial direction so as to be in contact with the carcass ply 61, the SIS main layer PL2 is used in the tire vulcanization process. The adhesion strength between the carcass 61 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

  In FIG.2 (b), the polymer laminated body PL is comprised from SIB main body layer PL3 as 1st layer PL1 and 2nd layer. When the polymer laminate PL is applied to an inner liner of a pneumatic tire, if the surface of the SIB main layer PL3 is disposed facing the outer side in the tire radial direction so as to be in contact with the carcass ply 61, in the tire vulcanization process, The adhesive strength between the main layer PL3 and the carcass 61 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

  In FIG. 2C, the polymer laminate PL is configured by laminating a first layer PL1, a SIS main layer PL2 and a SIB main layer PL3 as the second layer in the above order. When the polymer laminate PL is applied to an inner liner of a pneumatic tire, if the surface of the SIB main layer PL3 is disposed facing the outer side in the tire radial direction so as to be in contact with the carcass ply 61, in the tire vulcanization process, The adhesive strength between the main layer PL3 and the carcass ply 61 can be increased. Therefore, the obtained pneumatic tire can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

  In FIG.2 (d), polymer laminated body PL is comprised by laminating | stacking 1st layer PL1, SIB main body layer PL3 and SIS main body layer PL2 as a 2nd layer in the said order. When the polymer laminate PL is applied to the inner liner of a pneumatic tire, if the surface of the SIS main layer PL2 is disposed facing the outer side in the tire radial direction so as to be in contact with the carcass ply 61, in the tire vulcanization process, The adhesive strength between the main layer PL2 and the carcass ply 61 can be increased. Therefore, since the inner liner and the rubber layer of the carcass ply 61 are adhered well, it is possible to have excellent air permeation resistance and durability.

<Pneumatic tire manufacturing method>
A general manufacturing method can be used for the pneumatic tire of the present invention. An inner liner is manufactured using the polymer laminate PL. It can be manufactured by applying the inner liner to the raw tire of the pneumatic tire 1 and vulcanizing it together with other members. When the polymer laminate PL is arranged on the raw tire, the SIS main layer PL2 or the SIB main layer PL3, which is the second layer of the polymer laminate PL, is arranged outward in the tire radial direction so as to be in contact with the carcass ply 61. . With this arrangement, the adhesion strength between the SIS main layer PL2 or the SIB main layer PL3 and the carcass 6 can be increased in the tire vulcanization step. The obtained pneumatic tire can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

<Preparation of elastomer component>
The elastomer used for the first layer and the second layer of the present invention was prepared as follows.

(1) Isoprene-modified copolymer (1-1) Component A-1: (styrene / β-pinene) -isobutylene- (styrene / β-pinene) block copolymer (β-pinene content: 9.7 weight) %, Number average molecular weight (Mn): 103,000).

The manufacturing method of the said component A-1 is as follows.
After replacing the inside of the container of the 2 L separable flask with nitrogen, 31.0 mL of n-hexane and 294.6 mL of butyl chloride similarly dried using molecular syringes were added using a syringe, and the polymerization container was -70. After cooling in a dry ice / methanol mixing bath at 0 ° C., a Teflon (registered trademark) liquid feeding tube is placed in a pressure-resistant glass liquefied collection tube with a three-way cock containing 88.9 mL (941.6 mmol) of isobutylene monomer. And the isobutylene monomer was fed into the polymerization vessel by nitrogen pressure. 0.148 g (0.6 mmol) of p-dicumyl chloride and 0.07 g (0.8 mmol) of α-picoline were added. Further, 0.87 mL (7.9 mmol) of titanium tetrachloride was added to initiate polymerization. After stirring at the same temperature for 1.5 hours from the start of polymerization, 1 mL of the polymerization solution was extracted from the polymerization solution as a sample. Then, 10.4 g (99.4 mmol) of styrene monomer and 6.8 g (49.7 mmol) of β-pinene that had been cooled to −70 ° C. were uniformly stirred, and then added to the polymerization vessel. 45 minutes after adding styrene and β-pinene, about 40 mL of methanol was added to terminate the reaction. After distilling off the solvent from the reaction solution, it was dissolved in toluene and washed twice with water. The toluene solution was added to a large amount of methanol to precipitate the polymer, and the resulting product was vacuum dried at 60 ° C. for 24 hours. The molecular weight of the block copolymer obtained by GPC method was measured. The number average molecular weight (Mn) is 103,000, and Mw / Mn is 1.21.

  (1-2) Component A-2: (Styrene / β-pinene) -isobutylene- (styrene / β-pinene) block copolymer (β-pinene content: 5.3% by weight, number average molecular weight: 10,7000 ).

The manufacturing method of component A-2 is as follows.
After replacing the inside of the container of the 2 L separable flask with nitrogen, 31.0 mL of n-hexane and 294.6 mL of butyl chloride similarly dried using molecular syringes were added using a syringe, and the polymerization container was -70 ° C. After cooling in a dry ice / methanol mixing bath, a Teflon (registered trademark) feeding tube was placed in a pressure-resistant glass liquefied collection tube with a three-way cock containing 88.9 mL (941.6 mmol) of isobutylene monomer. Then, isobutylene monomer was fed into the polymerization vessel by nitrogen pressure. 0.148 g (0.6 mmol) of p-dicumyl chloride and 0.07 g (0.8 mmol) of α-picoline were added.

  Next, 0.87 mL (7.9 mmol) of titanium tetrachloride was added to initiate polymerization. After stirring at the same temperature for 1.5 hours from the start of polymerization, 1 mL of the polymerization solution was extracted from the polymerization solution as a sample. Then, 10.4 g (99.4 mmol) of styrene monomer cooled to −70 ° C. and 3.6 g (26.3 mmol) of β-pinene were uniformly stirred and then added to the polymerization vessel. About 40 mL of methanol was added 45 minutes after addition of styrene and β-pinene to terminate the reaction. After distilling off the solvent from the reaction solution, it was dissolved in toluene and washed twice with water. Further, the toluene solution was added to a large amount of methanol to precipitate a polymer, and the obtained polymer was vacuum-dried at 60 ° C. for 24 hours. The molecular weight of the block polymer obtained by GPC method was measured. The number average molecular weight (Mn) of the block copolymer is 107,000, and Mw / Mn is 1.23.

  (1-3) Component A-3: Styrene- (isobutylene / β-pinene) -styrene block copolymer (β-pinene content 5.3% by weight, number average molecular weight 10,9000).

The manufacturing method of component A-3 is as follows.
After the inside of the polymerization vessel of the 2 L separable flask was replaced with nitrogen, 31.0 mL of n-hexane and 294.6 mL of butyl chloride dried with molecular sieves were added using a syringe and the polymerization vessel was added. After cooling by placing in a -70 ° C dry ice and methanol mixed bath, 3.6 g (26.3 mmol) of β-pinene was added.

  Next, a liquid feeding tube made of Teflon (registered trademark) was connected to a pressure-resistant glass liquefied collection tube with a three-way cock containing 88.9 mL (941.6 mmol) of isobutylene monomer, and the isobutylene monomer was placed in the polymerization vessel by nitrogen pressure. Liquid was sent. Further, 0.148 g (0.6 mmol) of p-dicumyl chloride and 0.07 g (0.8 mmol) of α-picoline were added. Next, 0.87 mL (7.9 mmol) of titanium tetrachloride was further added to initiate polymerization. 45 minutes after the start of polymerization and 10.4 g (99.4 mmol) of styrene monomer cooled to −70 ° C. was added into the polymerization vessel. About 40 mL of methanol was added 45 minutes after the addition of styrene to terminate the reaction. After distilling off the solvent from the reaction solution, it was dissolved in toluene and washed twice with water. Further, the toluene solution was added to a large amount of methanol to precipitate a polymer, and the obtained polymer was vacuum-dried at 60 ° C. for 24 hours. The molecular weight of the block copolymer obtained by GPC method was measured. The number average molecular weight (Mn) of the block copolymer is 109,000, and Mw / Mn is 1.21.

(2) SIB (styrene-isobutylene block copolymer)
To a 2 L reaction vessel equipped with a stirrer, 589 mL of methylcyclohexane (dried with molecular sieves), 613 ml of n-butyl chloride (dried with molecular sieves), and 0.550 g of cumyl chloride were added. After cooling the reaction vessel to −70 ° C., 0.35 mL of α-picoline (2-methylpyridine) and 179 mL of isobutylene were added. Further, 9.4 mL of titanium tetrachloride was added to initiate polymerization, and the reaction was allowed to proceed for 2.0 hours while stirring the solution at -70 ° C. Next, 59 mL of styrene was added to the reaction vessel, and the reaction was continued for another 60 minutes, and then a large amount of methanol was added to stop the reaction. After removing the solvent and the like from the reaction solution, the polymer was dissolved in toluene and washed twice with water. This toluene solution was added to a methanol mixture to precipitate a polymer, and the obtained polymer was dried at 60 ° C. for 24 hours to obtain a styrene-isobutylene diblock copolymer (styrene component content: 15% by mass). , Weight average molecular weight: 70,000).

(3) SIBS (styrene-isobutylene-styrene block copolymer)
“Sibstar SIBSTAR 102T (Shore A hardness 25, styrene component content 25 mass%, weight average molecular weight: 100,000)” manufactured by Kaneka Corporation was used.

(4) SIS (styrene-isoprene-styrene block copolymer)
D1161JP (styrene component content 15 mass%, weight average molecular weight: 150,000) manufactured by Kraton Polymer Co., Ltd. was used.

  (5) “Exon Chlorobutyl 1066” manufactured by ExxonMobil Co., Ltd. was used for IIR.

<Adjustment of elastomer composition of first layer and second layer>
As shown in Tables 1 and 2, additives were blended into the elastomer component to prepare elastomer compositions for the first layer and the second layer.

(Note 1) Carbon black (CB): “Seast V” (N660, N ₂ SA: 27 m ² / g) manufactured by Tokai Carbon Co., Ltd.
(Note 2) Zinc oxide (ZnO): “Zinc Hana 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
(Note 3) Stearic acid: “Lunac stearate S30” manufactured by Kao Corporation.
(Note 4) Anti-aging agent: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 5) Vulcanization accelerator: “Noxeller DM” manufactured by Ouchi Shinsei Chemical Co., Ltd.
(Note 6) Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
(Note 7) Anti-sticking agent: C9 petroleum resin, Alcon P140 (Arakawa Chemical Industries, Ltd., softening point 140 ° C., weight average molecular weight Mw: 900).
(Note 8) Polyisoprene: “Tetrax 3T” (manufactured by Nippon Oil Corporation) (viscosity average molecular weight 30,000, weight average molecular weight, 49,000).

<Inner liner manufacturing method>
Based on the formulations in Tables 1 and 2, additives are added to thermoplastic elastomers such as isoprene-based modified copolymers, SIBS, SIS and SIB, Banbury mixer, kneader, twin screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 220 ° C.) to obtain an elastomer composition. Thereafter, an inner liner was produced with a T-die extruder (screw diameter: φ80 mm, L / D: 50, die lip width: 500 mm, cylinder temperature: 220 ° C.). The inner liner has a thickness of 0.3 mm (first layer: 0.25 mm, second layer: 0.05 mm).

<Manufacture of pneumatic tires>
A pneumatic tire is a 195 / 65R15 size tire having the basic structure shown in FIG. 1, and a polymer laminate of the first and second layers having the elastomer composition shown in Tables 1 to 5 is used as an inner liner. Tires were manufactured and then press molded at 170 ° C. for 20 minutes in the vulcanization process. After the tire vulcanization, the vulcanized tire was manufactured by cooling at 100 ° C. for 3 minutes without taking out from the mold.

<Comparative Examples 1-10>
Comparative Examples 1 and 3 and Comparative Examples 7 to 10 are examples in which a polymer laminate using SIBS for the first layer and SIS for the second layer was used for the inner liner. Comparative Example 2 is an example in which a polymer laminate using SIBS for the first layer and SIB for the second layer was used for the inner liner.

  Comparative Examples 4 and 5 are examples in which a tackifier is blended with SIBS in the first layer and SIS is used in the second layer. Comparative Example 6 is an example in which zinc oxide, stearic acid or the like is blended with SIBS in the first layer and SIS is used in the second layer.

<Examples 1 to 29>
Examples 1 to 6 are examples in which only the isoprene-based modified copolymer was used as the elastomer component in the first layer, and SIS and the isoprene-based modified copolymer (component A-1) were used in the second layer. Examples 7 to 9 are examples in which a mixture of isoprene-based modified copolymer and IIR was used as the elastomer component in the first layer, and SIS and isoprene-based modified copolymer (component A-1) were used in the second layer. It is.

  In Examples 10-15 and 25-29, isoprene-based modified copolymer (component A-1) is used as the elastomer component in the first layer. Among them, Examples 16 to 19, 25 to 27, and 29 use SIS for the second layer, and Example 28 uses SIB.

  Examples 20 to 24 use an isoprene-modified copolymer (component A-1) for the first layer and a mixture of SIS and isoprene-modified copolymer (component A-1) for the second layer. .

  It can be seen that Examples 1 to 29 are generally superior to Comparative Examples 1 to 10 in terms of vulcanization adhesion, flex crack growth, rolling resistance change rate, and static air reduction rate.

<Performance test>
The pneumatic tire manufactured as described above was evaluated for performance by the following method.

<Vulcanization adhesion>
The unvulcanized sheets of the first layer and the second layer are bonded together and vulcanized at 170 ° C. for 20 minutes to prepare a sample for measuring the vulcanized adhesive force. The peel strength was measured with a tensile tester to obtain a vulcanized adhesive strength. By the following formula, the vulcanization adhesive strength of each formulation was displayed as an index based on Comparative Example 1. In addition, it shows that vulcanization adhesive force is so high that the index | exponent of vulcanization adhesive force is large.

Vulcanization adhesion index = (vulcanization adhesion of each formulation) / (vulcanization adhesion of Comparative Example 1) × 100
<Bending crack growth test>
The durability running test was evaluated based on whether the inner liner was cracked or peeled off. The prototype tire is assembled to a JIS standard rim 15 × 6 JJ, the tire internal pressure is set to 150 KPa, which is lower than usual, the load is 600 kg, the speed is 100 km / h, the traveling distance is 20,000 km, the inside of the tire is observed, cracks, The number of peels was measured. Using Comparative Example 1 as a reference, the crack growth property of each formulation was displayed as an index. A larger index value indicates a smaller flex crack growth.

Flex crack growth index = (number of cracks in Comparative Example 1) / (number of cracks in each formulation) × 100
<Rolling resistance index>
Using a rolling resistance tester manufactured by Kobe Steel Co., Ltd., the prototype tire was assembled to a JIS standard rim 15 × 6JJ, and the temperature was set to room temperature (30 ° C.) under conditions of a load of 3.4 kN, an air pressure of 230 kPa, and a speed of 80 km / h. And rolling resistance was measured. And based on the following formula, the comparative example 1 was made into the reference | standard 100, and the rolling resistance change rate (%) of the Example was displayed by the index | exponent. It shows that rolling resistance is reduced, so that rolling resistance change rate is large.

Rolling resistance index = (Rolling resistance of Comparative Example 1) / (Rolling resistance of Example) × 100
<Static air pressure drop rate test>
The prototype tire is assembled to a JIS standard rim 15 × 6 JJ, filled with an initial air pressure of 300 kPa, and left at room temperature for 90 days to calculate the rate of decrease in air pressure. A smaller numerical value is preferable because the air pressure is less likely to decrease.

<Comprehensive judgment>
Judgment A means that all of the following conditions are satisfied.

(A) The vulcanization adhesive strength is 100 or more.
(B) Flexural crack growth is 100 or more.

(C) The rolling resistance change rate is 100 or more.
(D) Static air pressure reduction rate (% / month) is 2.6 or less.

  The decision B refers to a case where any one of the following conditions is satisfied. In the case of multiple determinations, the lower evaluation was adopted.

(A1) Vulcanization adhesion is lower than 100.
(B1) Flexural crack growth is lower than 100.

(C1) The rolling resistance change rate is lower than 100.
(D1) Static air pressure reduction rate (% / month) is 2.7 or more.

  The pneumatic tire of the present invention can be used as a pneumatic tire for trucks and buses, heavy machinery, etc. in addition to a pneumatic tire for passenger cars.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 2 tread part, 3 side wall part, 4 bead part, 5 bead core, 6 carcass ply, 7 belt layer, 8 bead apex, 9 inner liner, PL polymer laminated body, PL1 1st layer, PL2 SIS subject Layer, PL3 SIB main layer.

Claims (6)

A pneumatic tire having an inner liner on the inside of a carcass ply tire mounted between a pair of bead parts,
The inner liner is composed of a first layer disposed inside the tire and a second layer disposed so as to contact the rubber layer of the carcass ply,
At least one of the first layer and the second layer is an isobutylene block copolymer comprising a polymer block (A) mainly composed of isobutylene and a polymer block (B) mainly composed of an aromatic vinyl compound. The pneumatic tire is an elastomer composition including an isobutylene-based modified copolymer, which is a random copolymer in which at least one block includes β-pinene.   2. The pneumatic tire according to claim 1, wherein the elastomer composition of the first layer is 10% by mass or more and 100% by mass or less of an isobutylene-based modified copolymer in an elastomer component.   The pneumatic tire according to claim 1 or 2, wherein the elastomer composition of the second layer is an isobutylene-based modified copolymer in an amount of 5% by mass to 80% by mass in the elastomer component.   The pneumatic tire according to any one of claims 1 to 3, wherein the isobutylene-modified copolymer has a β-pinene content of 0.5 to 25% by weight.   The isobutylene modified copolymer has a weight average molecular weight Mw of 30,000 to 300,000 and a molecular weight distribution value (weight average molecular weight Mw / number average molecular weight Mn) of 1.3 or less. The pneumatic tire according to any one of claims 1 to 4.   The isobutylene-based modified copolymer contains β-pinene in a styrene block of a styrene-isobutylene-styrene block copolymer, a styrene-isoprene-styrene block copolymer or a styrene-isobutylene block copolymer. The pneumatic tire according to 1.

Images