JP2012116392A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having an inner liner for improving air permeation resistance, bending fatigue performance and crack resistance.SOLUTION: The inner liner 9 of this pneumatic tire 1 is constituted of a polymer laminate body constituted of a first layer having a thickness of 0.05-0.6 mm constituted of a polymer composition including an organizing treatment viscosity mineral by 0.1-50 mass% to a polymer mixture of 100 pts.mass including SIBS of 99-60 mass% and a polyamide-based polymer of 1-40 mass% including polyamide in a molecular chain and having Shore D hardness of 70 or less and a second layer having a thickness of 0.01-0.3 mm including at least any of SIS and SIB. The second layer is arranged so as to contact with a rubber layer of a carcass ply 6, and the inner liner 9 is thinner in an average thickness of a buttress area Rs ranging over a corresponding position Lu of the belt layer end from a tire maximum width position Le than an average thickness of a bead area Rb ranging over a bead toe Lt from the tire maximum width position Le.

Description

  The present invention relates to a pneumatic tire provided with an inner liner.

  In recent years, tires have been reduced in weight due to a strong social demand for lower fuel consumption of vehicles. Among the tire members, an inner liner that is arranged on the inner side in the tire radial direction and has the function of improving the air permeation resistance by reducing the amount of air leakage (air permeation amount) from the inside to the outside of the pneumatic tire. However, weight reduction has come to be performed.

  Currently, the use of butyl rubber containing 70-100% by weight of butyl rubber and 30-0% by weight of natural rubber as the rubber composition for the inner liner is used to improve the air permeation resistance of the tire. . In addition to butylene, the butyl rubber contains about 1% by mass of isoprene, which, together with sulfur, vulcanization accelerator, and zinc white, enables co-crosslinking with adjacent rubber. 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, in order to reduce the weight of the tire, it has been proposed to use a thermoplastic elastomer, which is superior in air permeation resistance as compared to butyl rubber, and can reduce the thickness of the inner liner, for the inner liner. However, if the inner liner using thermoplastic elastomer is thinner than butyl rubber, it will not be possible to achieve both air permeability and weight reduction, and the strength of the inner liner will be reduced, and the vulcanization process will be reduced. The inner liner may break due to the heat and pressure of the Prader. Furthermore, the thermoplastic elastomer having a relatively low strength has a problem that cracks are likely to occur in the inner liner in a buttress portion that is subjected to repeated large shear deformation during running of the tire.

  Patent Document 1 discloses a laminate for improving the adhesion between the inner liner and the rubber layer. By providing adhesive layers on both sides of the inner liner, the adhesive layers come into contact with each other at the overlapping portion of the inner liner and are firmly bonded by heating, so that the air pressure retention is improved. However, this adhesive layer for overlapping the inner liner comes into contact with the bladder in a heated state in the vulcanization process, and there is a problem that it adheres to and adheres to the bladder.

  In Patent Document 2, a mixture of a nylon resin having good air permeability and butyl rubber is prepared by dynamic crosslinking to produce an inner liner having a thickness of 100 μm. However, nylon resin is hard at room temperature and unsuitable as an inner liner for tires. In addition, the vulcanization adhesion to the rubber layer is not performed only with the mixture obtained by the dynamic crosslinking. Therefore, an adhesive layer for vulcanization is required in addition to the inner liner. Therefore, the structure of the inner liner member is complicated and the number of processes is increased. , Disadvantageous in terms of productivity.

  In Patent Document 3, a flexible gas barrier layer is prepared by dispersing maleic anhydride-modified hydrogenated styrene-ethylene-butadiene-styrene block copolymer in an ethylene-vinyl alcohol copolymer having good air barrier properties. . Further, the thermoplastic polyurethane layer is sandwiched sandwiched, and further, rubber glue (70/30 of butyl rubber / natural rubber is dissolved in toluene) is applied to the surface to be bonded to the tire rubber to produce an inner liner. However, the modified ethylene-vinyl alcohol copolymer dispersed in a flexible resin has low adhesive strength and may be peeled off from the thermoplastic polyurethane layer. In the modified ethylene-vinyl alcohol copolymer dispersed with a flexible resin, the flexible resin is dispersed, but the EVOH of the matrix is poor in bending fatigue and breaks during running of the tire. Furthermore, although rubber paste is applied to the surface to be bonded to the tire rubber, a process different from the normal inner liner process is required, resulting in poor productivity.

Patent Document 4 describes a pneumatic tire having an air permeation preventive layer made of a thermoplastic elastomer composition containing a thermoplastic resin or a thermoplastic resin and an elastomer inside a carcass layer. It has been proposed that the average thickness Gs of the air permeation preventive layer in the large region Ts is made thinner than the tire maximum width and the average thickness Gf of the air permeation preventive layer in the bead toe region Tf to improve the bending durability. Yes. However, in such a configuration, peeling between the rubber layer of the carcass ply and the air permeation preventive layer may occur.

JP-A-9-19987 Patent No. 2999188 JP 2008-24219 A JP 2008-174037 A

  An object of the present invention is to provide a pneumatic tire including an inner liner that improves air permeation resistance, bending fatigue resistance, and crack resistance.

  The pneumatic tire of the present invention includes an inner liner on the inner side of the tire, and the inner liner is a shore containing 99 to 60% by mass of a styrene-isobutylene-styrene triblock copolymer and polyamide in a molecular chain. The thickness of 0.05 to 50 parts comprising a polymer composition containing 0.1 to 50 parts by weight of an organically treated viscosity mineral with respect to 100 parts by weight of a polymer mixture containing 1 to 40% by weight of a polyamide-based polymer having a D hardness of 70 or less. A first layer having a thickness of 0.6 mm, and a second layer having a thickness of 0.01 to 0.3 mm including at least one of a styrene-isoprene-styrene triblock copolymer and a styrene-isobutylene diblock copolymer. The second layer is disposed so as to be in contact with the rubber layer of the carcass ply, and the inner liner is a tie. Than the average thickness Gb of bead region Rb over the bead toe from the maximum width position, wherein the average thickness Gs of buttress region Rs over the corresponding positions Lu of the belt layer end from the tire maximum width position is thin.

  The ratio (Gs / Gb) of the average thickness Gs of the buttress area of the inner liner to the average thickness Gb of the bead area is preferably 0.3 to 0.75.

  The average thickness Gs of the buttress region of the inner liner is preferably 0.05 to 0.45 mm. The polymer mixture preferably contains 15 to 40% by mass of an ethylene-vinyl alcohol copolymer.

  The styrene-isobutylene-styrene triblock copolymer preferably contains 10 to 30% by mass of styrene. The polyamide polymer is preferably a block copolymer comprising a polyamide component and a polyether component.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire provided with the inner liner which improves air permeation resistance, bending fatigue resistance, and crack resistance can be provided.

It is typical sectional drawing which shows the right half of the pneumatic tire in one embodiment of this invention. It is a schematic sectional drawing of the inner liner in the pneumatic tire of the present invention. It is a schematic sectional drawing of the inner liner in the pneumatic tire of the present invention. It is a schematic sectional drawing of the inner liner in the pneumatic tire of the present invention. It is a schematic sectional drawing of the inner liner in the pneumatic tire of the present invention.

<Pneumatic tire>
The present invention is a pneumatic tire provided with an inner liner on the inside of the tire, and the inner liner is formed of a polymer laminate of two or more layers including at least a first layer and a second layer. The first layer is composed of 99 to 60% by mass of a styrene-isobutylene-styrene triblock copolymer (hereinafter also referred to as “SIBS”), and a polyamide-based polymer 1 to 40 having a Shore D hardness of 70 or less and containing polyamide in the molecular chain. It consists of a polymer composition containing 0.1 to 50 parts by mass of an organically treated viscosity mineral with respect to 100 parts by mass of a polymer mixture containing 5% by mass, and has a thickness in the range of 0.05 mm to 0.6 mm. The second layer includes at least one of styrene-isoprene-styrene triblock copolymer (SIS) and styrene-isobutylene diblock copolymer (SIB), and has a thickness of 0.01 mm to 0.3 mm. The second layer is disposed so as to contact the rubber layer of the carcass ply.

  An embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the right half of a pneumatic tire for passenger cars. The 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. Also, a carcass ply 6 provided from one bead portion 4 to the other bead portion, with both ends folded back and locked around the bead core 5, 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 °. To be arranged. 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. The carcass ply has an organic fiber cord made of polyester, nylon, aramid or the like arranged at approximately 90 ° in the tire circumferential direction. The region surrounded by the carcass ply and its folded portion has a sidewall extending from the upper end of the bead core 5 A bead apex 8 extending in the direction is arranged. Further, an inner liner 9 extending from one bead portion 4 to the other bead portion 4 is disposed on the inner side in the tire radial direction of the carcass ply 6.

  In the present invention, from the average thickness Gb of the inner liner 9 in the bead area Rb extending from the tire maximum width position Le to the bead toe Lt, the inner liner 9 in the buttress area Rs extending from the tire maximum width position Le to the corresponding position Lu at the belt layer end. The average thickness Gs is made thin.

  By reducing the thickness of the inner liner in the buttress region Rs, even when shear deformation occurs due to repeated bending deformation in this region during tire running, the stress can be relieved and cracking can be prevented. can do.

  In order to effectively relieve the stress due to bending deformation, the ratio (Gs / Gb) of the average thickness Gs of the buttress region Rs of the inner liner to the average thickness Gb of the bead region Rb is 0.3 to 0.75. More preferably, it is 0.5 to 0.7. Further, in order to maintain the air pressure holding performance and also have the effect of relaxing the stress in the buttress area, it is desirable that the average thickness Gs of the buttress area Rs of the inner liner is 0.05 to 0.45 mm.

<Polymer laminate>
In one embodiment of the present invention, the polymer laminate includes a first layer containing 99 to 60 parts by mass of SIBS and a second layer containing at least one of SIS and SIB, and the thickness of the first layer is 0. 0.05 mm to 0.6 mm, and the thickness of the second layer is 0.01 mm to 0.3 mm.

<First layer>
In one embodiment of the present invention, the first layer is composed of 100 parts by mass of a polymer mixture containing 99 to 60% by mass of SIBS and 1 to 40% by mass of a polyamide-based polymer having a Shore D hardness of 70 or less containing polyamide in the molecular chain. On the other hand, it consists of a polymer composition containing 0.1 to 50 parts by mass of an organically treated viscosity mineral. Here, the “organization-treated viscosity mineral” means a layered viscosity mineral obtained by intercalating an organic compound. Due to the isobutylene block of SIBS, the polymer composition comprising SIBS has excellent air permeation resistance. Therefore, when a polymer film containing SIBS is used for the inner liner, a pneumatic tire having excellent air permeation resistance can be obtained.

  Further, SIBS has excellent durability because its molecular structure other than aromatic is completely saturated, thereby preventing deterioration and hardening. On the other hand, due to the contribution from the polyamide portion of the polyamide-based polymer, the polymer composition can be bonded to the unsaturated polymer, and the adhesion to the adjacent rubber is improved.

  Furthermore, in one embodiment of the present invention, when an unvulcanized polymer sheet made of the polymer mixture is used for an inner liner, in order to ensure air permeation resistance by containing SIBS, for example, halogenated butyl rubber or the like. The amount of use can be reduced even when the high specific gravity halogenated rubber which has been used for imparting air permeation resistance is not used or used. As a result, the weight of the tire can be reduced, and the effect of improving fuel consumption can be obtained. Further, the halogenated rubber has a problem that the adhesion between the ply cord of the pneumatic tire and the rubber is deteriorated due to the halogen in the rubber. In the present invention, the amount of the halogenated rubber is used. Therefore, the durability of the pneumatic tire can be improved by improving the adhesion between the ply cord and the polymer mixture.

  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.

<Styrene-isobutylene-styrene triblock copolymer (SIBS)>
In the polymer composition according to one embodiment of the present invention, the SIBS content in the polymer mixture is 99 to 60% by mass. When the SIBS content is 60% by mass or more, excellent air permeation resistance and durability can be obtained. Moreover, it is preferable that this content shall be 95-80 mass% at the point from which air permeation resistance and durability become more favorable.

  SIBS generally contains 10-40% by weight of styrene. The content of the styrene is preferably 10 to 30% by mass in terms of better air permeation resistance and durability.

  SIBS preferably has a molar ratio of isobutylene to styrene (isobutylene / styrene) of 40/60 to 95/5 from the viewpoint of rubber elasticity of the copolymer. In SIBS, the degree of polymerization of each block is about 10,000-150,000 for isobutylene and 10,000-30,000 for styrene in terms of rubber elasticity and handling (becomes liquid when the degree of polymerization is less than 10,000). It is preferably about 000.

  The molecular weight of the SIBS is not particularly limited, but it is preferable that the weight average molecular weight by GPC measurement is 50,000 to 400,000 from the viewpoints of fluidity, molding process, rubber elasticity and the like. If the weight average molecular weight is less than 50,000, the tensile strength and the tensile elongation may be lowered, and if it exceeds 400,000, the extrusion processability may be deteriorated. From the viewpoint of improving air permeation resistance and durability, SIBS has a styrene component content in SIBS of 10 to 30% by mass, preferably 14 to 23% by mass.

  SIBS can be obtained by a general vinyl compound polymerization method, for example, a living cationic polymerization method.

  For example, JP-A-62-48704 and JP-A-64-62308 disclose that living cationic polymerization of isobutylene and other vinyl compounds is possible. By using isobutylene and other compounds as vinyl compounds, It is disclosed that a polyisobutylene-based block copolymer can be produced. In addition, methods for producing vinyl compound polymers by the living cationic polymerization method are disclosed in, for example, U.S. Pat. No. 4,946,899, U.S. Pat. No. 5,219,948, and JP-A-3-174403. Are listed.

  Since SIBS does not have double bonds other than aromatics in the molecule, it is more stable to ultraviolet light than polymers having double bonds in the molecule such as polybutadiene, and therefore weather resistance is high. It is good. Furthermore, although it has no double bond in the molecule and is a saturated rubber-like polymer, the refractive index (nD) at 20 ° C. of light with a wavelength of 589 nm is the Polymer Handbook (1989: Wiley). (Polymer Handbook, Willy, 1989)) is 1.506. This is significantly higher than other saturated rubbery polymers such as ethylene-butene copolymers.

<Polyamide polymer>
In the polymer composition according to one embodiment of the present invention, the content of the polyamide-based polymer in the polymer mixture is 1 to 40% by mass. When the content of the polyamide-based polymer is 40% by mass or less, a polymer mixture in which durability and adhesion are compatible can be obtained. Moreover, it is preferable that this content shall be 3-20 mass% at the point which can ensure durability and adhesiveness and can mix | blend more SIBS and ethylene-vinyl alcohol copolymer which are excellent in air permeation resistance.

  The polyamide polymer is preferably a polyamide polymer having a Shore D hardness of 70 or less. If the Shore D hardness exceeds 70, it is not preferable because the cracking property at the time of bending and moving of the tire is inferior. The Shore D hardness is preferably in the range of 15 to 70, more preferably in the range of 18 to 70, more preferably in the range of 20 to 70, and particularly preferably in the range of 25 to 70.

  The polyamide-based polymer preferably contains 50% by mass or more of the following polyetheramide elastomer (X).

  Polyetheramide elastomer (X): a polyamide component obtained by polymerizing a triblock polyetherdiamine compound (A) represented by the following formula (I), a polyamide-forming monomer (B), and a dicarboxylic acid compound (C) And a block copolymer comprising a polyether component.

(In the formula, a and b are 1 to 20, and c is 4 to 50.)
The polyamide-forming monomer (B) is preferably represented by the following formula (II) and / or the following formula (III).

(In the formula, R ¹ represents a linking group containing a hydrocarbon chain.)

(In the formula, R ² represents a linking group containing a hydrocarbon chain.)
The dicarboxylic acid compound (C) is preferably represented by the following formula (IV) and / or an aliphatic dicarboxylic acid compound and / or an alicyclic dicarboxylic acid compound.

(In the formula, R ³ represents a linking group containing a hydrocarbon chain, and y represents 0 or 1.)
When the polyamide polymer is a polyamide polymer having a hard segment derived from the polyamide component and a soft segment derived from the polyether component, the crystallinity is lowered, and therefore, the elongation at break EB is high and flexible from a low temperature to a high temperature region. A polyamide-based polymer exhibiting properties can be obtained.

  In addition, since the polyamide-based polymer has improved fluidity at the tire vulcanization temperature (140 to 180 ° C.) and wettability with the uneven surface, it can exhibit an excellent effect in adhesion to the adjacent rubber.

In one embodiment of the present invention, a known polyamide polymer can be used as the polyamide polymer. As the polyamide-based polymer, at least one selected from a polyamide block composed of at least one aliphatic nylon selected from nylon 6, nylon 66, nylon 11, and nylon 12, and polyoxyethylene, polyoxypropylene, and polyoxybutylene. An elastomer composed of a polyether block of

  The method for producing the polyamide polymer is not particularly limited, and methods disclosed in JP-A-56-65026, JP-A-55-133424, JP-A-63-95251 and the like can be used. it can.

<Polymer mixture>
The polymer mixture used in one embodiment of the present invention may contain other polymers or resins in addition to SIBS and a polyamide-based polymer having a Shore D hardness of 70 or less containing polyamide in the molecular chain. For example, in addition to SIBS and polyamide polymer, nylon, PET, chlorobutyl rubber, natural rubber, ethylene propylene-diene terpolymer (EPDM), styrene butadiene rubber (SBR), butadiene rubber, isoprene rubber, butyl rubber, halogen Butyl rubber, acrylonitrile-butadiene rubber (NBR) and the like can be blended.

  The polymer mixture used in one embodiment of the present invention preferably contains an ethylene-vinyl alcohol copolymer within a range of 15 to 40% by mass. When the content of the ethylene-vinyl alcohol copolymer in the polymer mixture is 15% by mass or more, the gas barrier property of the polymer composition is ensured. Further, when the content is 40% by mass or less, kneadability at the time of producing the polymer composition is secured, and basic performance such as mechanical strength is secured in the inner liner of the tire. The content is preferably 20% by mass or more, and more preferably 25% by mass or more. Further, from the viewpoint of tire durability, the content is preferably 30% by mass or less.

  The ethylene-vinyl alcohol copolymer has the following general formula (V)

(Wherein, m and n are each independently 1 to 100, and x is 1 to 1000), and is preferably an ethylene-vinyl alcohol copolymer.

  The ethylene-derived portion of the ethylene-vinyl alcohol copolymer provides good compatibility with other components in the polymer mixture, and the ethylene-vinyl alcohol copolymer is present in a fine dispersion size in the polymer composition. be able to. On the other hand, the ethylene-vinyl alcohol copolymer has good gas barrier properties due to the contribution of vinyl alcohol-derived sites. That is, in the present invention, even when the inner liner of the tire is thinned, the ethylene-vinyl alcohol copolymer excellent in gas barrier properties is dispersed in an island shape with a fine size in the polymer composition. Good gas barrier properties are expressed. As a result, the weight of the tire can be reduced, and the effect of improving fuel consumption can be obtained.

  In the general formula (V), m and n are 1 or more in order to constitute an ethylene-vinyl alcohol copolymer. On the other hand, when m and n are each 100 or less, an ethylene-vinyl alcohol copolymer in which compatibility with other components in the polymer mixture and gas barrier properties are compatible is obtained. It is preferable that m is further 5 or more from the viewpoint of better compatibility with other components in the polymer mixture. Moreover, it is preferable that n is further set to 5 or more from the viewpoint of better gas barrier properties. On the other hand, m is preferably 95 or less, more preferably 80 or less, from the viewpoint that it is difficult to impair the gas barrier property due to the vinyl alcohol-derived site. Further, n is preferably 95 or less, and more preferably 80 or less, from the viewpoint that it is difficult to impair the expression of good compatibility with the polymer mixture due to the ethylene-derived site.

  In the general formula (V), x is 1 or more in order to constitute an ethylene-vinyl alcohol copolymer. On the other hand, when x is 1000 or less, kneadability at the time of producing the polymer composition is ensured, and a polymer composition in which the ethylene-vinyl alcohol copolymer is uniformly dispersed is obtained. In terms of good compatibility with other components in the polymer mixture and good gas barrier properties, x is preferably 10 or more, and in terms of good kneadability, x is further It is preferably 500 or less, more preferably 100 or less.

  The ethylene-vinyl alcohol copolymer represented by the general formula (V) may be contained in the polymer composition in the form of a copolymer with other components. In this case, the ethylene-vinyl alcohol copolymer The polymer content means the content of the structural portion represented by the general formula (V).

  The molecular structure of the ethylene-vinyl alcohol copolymer can be confirmed by, for example, an infrared absorption spectrum (IR) or a nuclear magnetic resonance spectrum (NMR).

<Polymer composition>
The polymer composition according to an embodiment of the present invention includes an organically treated clay mineral in addition to SIBS and a polyamide-based polymer having a Shore D hardness of 70 or less including polyamide in a molecular chain.

<Organized clay mineral>
The organically treated clay mineral is a layered clay mineral obtained by intercalating an organic compound. When the organic compound intercalates between the layers of the layered clay mineral, the layers are expanded and the dispersibility into the polymer is improved.

  The layered clay mineral is a kind of layered silicate mineral, and the crystal structure is a stack of three layers of silicate tetrahedral layer-alumina octahedral layer-silicate tetrahedral layer, and the unit layer has a thickness of about 10 mm (1 nm), It has a very thin plate shape with a spread of 0.1 to 1 μm.

A typical example of the layered clay mineral is montmorillonite. Montmorillonite becomes positive charge deficient in a part of Al is the center atom of the alumina octahedral layer in the crystal structure is replaced by Mg, although each crystal layer itself is negatively charged, the crystal layers Na ⁺・ Insufficiency of charge is neutralized by sandwiching cations such as K ⁺ , Ca ²⁺ and Mg ^2+, and a stable state is obtained. Therefore, montmorillonite exists in a state in which a number of crystal layers are overlapped.

  When water contacts the surface of the montmorillonite plate-like crystal layer, water molecules hydrate to the exchangeable cations between the layers, and the layers expand. Further, by intercalating an organic compound between layers using the cation exchange property of montmorillonite, the layers are expanded and the dispersibility in organic solvents and polymers is improved.

  Examples of layered clay minerals include montmorillonite (especially sodium montmorillonite, magnesium montmorillonite and calcium montmorillonite), bentonite, kaolinite, nonlite, beidellite, vorconskite, hectorite, saponite, sauconite, sobokite, stevensite, subfolder Mite minerals such as phyllosilicates such as smite, vermiculite and other smectite clays, illite and illite / smectite mixtures (lectretite, talosobite, ladykite and mixtures of the above clay compounds with illite) or attapulgite and sepiolite hydrotals Site-based layered compounds are exemplified. Of these, smectite clay is preferable, and montmorillonite clay is particularly preferable. Bentonite containing a smectite clay mineral may be used. These layered clay minerals are generally obtained by collecting natural minerals and performing a predetermined refining operation. These synthetic clays can be used interchangeably.

  Examples of the organic compound that can be used as an intercalant include organic compounds having a polar group that is easily ionized in the molecule. An organic compound having a polar group causes a strong interaction with the surface of a layer covered with negative ions such as oxygen ions of smectite clay minerals, and enters (intercalates) the layered clay mineral. It is thought to expand and expand.

  As the organic compound, those having an alkyl group having 6 or more carbon atoms and having a polar group ionizing at the terminal are preferable. Examples thereof include those having a hydroxyl group or a carboxyl group, aldehydes, amines, amides, or quaternary ammonium salts.

  Examples of the organic compound having a hydroxyl group include aliphatic alcohols such as octyl alcohol and nonyl alcohol, alcohols such as aromatic alcohol substituted with an alkyl group, and phenols.

  Examples of organic compounds having a carboxyl group include linear aliphatics such as stearic acid, palmitic acid, and lauric acid, linear alkenoic acids such as oleic acid, dienoic acids such as linoleelaidic acid, and polyunsaturated acids such as trienoic acid. Examples include aliphatic acids.

Examples of aldehydes include hexyl aldehyde.
As amines or amides, polar organic compounds having one or more amines or amides, such as alkylamines, aminocycloalkanes and aminocycloalkane substituents, cycloaliphatic diamines, aliphatic amines, alkylaromatic amines, alkyldiaryls Examples include amines, aliphatic amides, etc., including primary, secondary, and / or tertiary amines or amides. Of these, alkylamines, aliphatic amines, alkylaromatic amines, and alkyldiarylamines are preferable. The said organic compound can be used individually or in mixture of 2 or more types.

  Preferred amines include 1-hexylamine, 1-heptylamine, 1-octylamine, 1-nomylamine, 1-dodecylamine, 1-hexadecylamine, 1-octadecylamine, primary amines such as oleylamine, di-n Secondary amines such as dodecylamine, di-n-hexadecylamine, di-n-octadecylamine, dimethyl-n-octylamine, dimethyl-n-decylamine, dimethyl-n-tetradecylamine, dimethyl-n-hexa Tertiary amines such as decylamine, dimethyl-n-octadecylamine, dimethyloleylamine, di-n-decylmethylamine dicocoalkylmethylamine, tri-n-octylamine, tri-n-decylamine, tri-n-hexadecyl Aliphatic amines such as amines can be mentioned.

  Preferable amides include hexylamide, heptylamide, octylamide, nonylamide, lauramide, myristamide, palmitamide, steramide, palmamid, oleamide, linoleamide and the like.

  Moreover, what has a nitrile group or a lactam group, a pyridine, ester, surfactant, ethers etc. can also be used as an organic compound which has a polar group.

  Examples of the quaternary ammonium salt include dimethyl distearyl ammonium salt, trimethyl stearyl ammonium salt, dimethyl dioctadecyl ammonium, dimethyl benzyl octadecyl ammonium, and trimethyl octadecyl ammonium.

  As a method for intercalating an organic compound into the layered clay mineral, a known method can be employed. For example, in order to contact a montmorillonite clay mineral and an organic compound, the layered clay mineral is preliminarily made to contain 10% by mass to 20 times the mass of water, and then the organic compound and the montmorillonite clay mineral are contacted. There is a method for obtaining an organically treated clay mineral.

  The cation exchange amount of the organic compound in the organically treated clay mineral is preferably 50 to 200 meg / 100 g.

  The compounding amount of the organically treated clay mineral is 0.1 to 50 parts by mass, more preferably 0.5 to 30 parts by mass with respect to 100 parts by mass of the polymer mixture. When the blending amount of the organically treated clay mineral is less than 0.1 parts by mass, the air permeability and the tensile properties at high temperature of the polymer composition are lowered. On the other hand, when the blending amount of the organically treated clay mineral exceeds 50 parts by mass, the hardness of the polymer composition becomes too high and the bending fatigue property is lowered.

<Additive of polymer composition>
The polymer composition in one embodiment of the present invention includes general rubber compositions such as other reinforcing agents, vulcanizing agents, vulcanization accelerators, various oils, anti-aging agents, softening agents, plasticizers, and coupling agents. Various compounding agents and additives blended in the product can be blended. Examples of these additives include stearic acid, zinc oxide, anti-aging agent, and vulcanization accelerator.

<Second layer>
In the present invention, the second layer is also referred to as a SIS layer composed of a styrene-isoprene-styrene triblock copolymer (hereinafter also referred to as “SIS”) and a styrene-isobutylene diblock copolymer (hereinafter referred to as “SIB”). At least one of the SIB layers.

  Since the isoprene block of the styrene-isoprene-styrene triblock 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.

  The molecular weight of SIS is not particularly limited, but from the viewpoint of rubber elasticity and moldability, the weight average molecular weight by GPC measurement is preferably 100,000 to 290,000. 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. It is preferable that content of the styrene component in SIS is 10-30 mass% from a viewpoint of adhesiveness, 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.

  SIS can be obtained by a general vinyl compound polymerization method, for example, by 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 diblock 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.

  Said SIB can be obtained by the general polymerization method of a vinyl compound, for example, can be obtained by the living cation polymerization method. For example, in International Publication No. 2005/033035, methylcyclohexane, n-butyl chloride and cumyl chloride are added to a stirrer, cooled to −70 ° C., reacted for 2 hours, and then a large amount of methanol is added. A production method is disclosed in which the reaction is stopped and vacuum-dried at 60 ° C. to obtain SIB.

  The SIB layer can be obtained by forming SIB into a film by an ordinary method of forming a thermoplastic resin or thermoplastic elastomer into a film such as extrusion molding or calendering.

  The thickness of the second layer is 0.01 mm to 0.3 mm. Here, the thickness of the second layer is the thickness of the SIS layer when the second layer is composed of only the SIS layer, and the thickness of the SIB layer when the second layer is composed of only the SIB layer. When the two layers are composed of two layers of the SIS layer and the SIB layer, it means the total thickness of the SIS layer and the SIB layer. When 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 increases and the fuel efficiency performance decreases. The thickness of the second layer is further preferably 0.05 to 0.2 mm.

<Form of polymer laminate>
Various structures can be adopted as the structure of the polymer laminate used for the inner liner in the present invention. These forms will be described with reference to FIGS. 2 to 5 which are schematic sectional views of the inner liner.

Form 1
As shown in FIG. 2, the polymer laminate 10 includes a first layer 11 containing SIBS and a SIS layer 12 as a second layer. When the polymer laminate 10 is applied to an inner liner of a pneumatic tire, the SIS layer 12 and the carcass are disposed in the tire vulcanization process when the SIS layer 12 is installed so as to be in contact with the carcass ply 61 toward the outer side in the tire radial direction. Adhesive strength with 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.

Form 2
As shown in FIG. 3, the polymer laminate 10 includes a first layer 11 containing SIBS and an SIB layer 13 as a second layer. When the polymer laminate 10 is applied to an inner liner of a pneumatic tire, if the surface of the SIB layer 13 is disposed facing the outer side in the tire radial direction so as to be in contact with the carcass ply 61, the SIB layer 13 and the carcass 61 can be increased in adhesive strength. 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.

Form 3
As shown in FIG. 4, the polymer laminate 10 is configured by laminating a first layer 11 containing SIBS, a SIS layer 12 as a second layer, and an SIB layer 13 in this order. When the polymer laminate 10 is applied to the inner liner 61 of a pneumatic tire, if the surface of the SIB layer 13 is installed 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 layer 13 and the carcass ply 6 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.

Form 4
As shown in FIG. 5, the polymer laminate 10 is configured by laminating a first layer 11 containing SIBS, an SIB layer 13 as a second layer, and an SIS layer 12 in this order. When the polymer laminate 10 is applied to an inner liner of a pneumatic tire, when the surface of the SIS layer 12 is disposed so as to contact the carcass ply 61 toward the outer side in the tire radial direction, in the tire vulcanization process, the SIS layer 12 and the carcass ply 61 can be increased in adhesive strength. Therefore, the obtained pneumatic tire 1 can have excellent air permeation resistance and durability because the inner liner and the rubber layer of the carcass ply 61 are well bonded.

<Method for producing polymer laminate>
The polymer laminate of the inner liner used for the pneumatic tire of the present invention can be manufactured, for example, by the following method.

  First, as a material constituting the first layer, SIBS, polyamide-based polymer, organically treated viscosity mineral, and various additives as necessary are put into a twin screw extruder at about 150 to 280 ° C. and 50 to 300 rpm. The mixture is kneaded under conditions to obtain pellets of a polymer composition in which SIBS, a polyamide-based polymer, an organically treated viscosity mineral, and various additives added as necessary are dynamically cross-linked.

  In the twin screw extruder, SIBS, which is a thermoplastic resin composition, becomes a matrix phase and the rubber component becomes an island phase and is dispersed. Further, in the twin-screw extruder, the rubber component and the additive component react, and the rubber component that is an island phase undergoes a crosslinking reaction. This is called dynamic crosslinking because the rubber component is dynamically crosslinked in a twin screw extruder. Even if the rubber component is cross-linked in the twin-screw extruder, the matrix phase of the system is composed of a thermoplastic resin component, so that the shear viscosity of the entire system is low and extrusion processing is possible.

  The pellets of the dynamically crosslinked polymer composition obtained by the twin-screw extruder have the rubber component crosslinked, but the thermoplastic resin component of the matrix phase retains the plasticity, and produces the plasticity of the entire system. Playing a role. For this reason, since plasticity is exhibited even in T-die extrusion, it can be formed into a sheet shape.

  Furthermore, since the rubber component of the dynamically cross-linked polymer composition pellets is cross-linked, the polymer laminate manufactured using the pellets is applied to the inner liner to produce a pneumatic tire. Even if the tire is heated, the polymer composition of the inner liner can be prevented from entering the carcass layer.

  The polymer composition thus obtained and at least one of SIS and SIB are subjected to lamination extrusion such as laminate extrusion or coextrusion in the order described in any of forms 1 to 4, for example, to obtain a desired thickness. The polymer laminate is obtained.

<Pneumatic tire manufacturing method>
The pneumatic tire of the present invention can be manufactured using, for example, the following general manufacturing method. The polymer laminate 10 produced as described above can be produced by applying it to the inner liner of the raw tire of the pneumatic tire 1 and vulcanizing it together with other members. When the polymer laminate 10 is arranged on the green tire, the SIS layer 12 or the SIB layer 13 that is the second layer of the polymer laminate 10 is arranged outward in the tire radial direction so as to be in contact with the carcass ply 61. When arranged in this manner, the adhesive strength between the SIS layer 12 or the SIB layer 13 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.

  In order to adjust the thickness of the inner liner in the bead region Rb and the buttress region Rs, for example, a profile is attached to the extrusion opening of the polymer sheet, and an integrated sheet having a thin buttress region thickness Gs is prepared. This is arranged on the inner surface of the tire as an inner liner.

  The rubber layer of the carcass ply used in the pneumatic tire of the present invention is composed of generally used rubber components such as natural rubber, polyisoprene, styrene-butadiene rubber, polybutadiene rubber, and fillers such as carbon black and silica. Can be used.

  Next, the raw tire is mounted on a mold, and heated with pressure from 150 to 180 ° C. for 3 to 50 minutes to obtain a vulcanized tire. Next, it is preferable to cool the obtained vulcanized tire at 50 to 120 ° C. for 10 to 300 seconds.

  A pneumatic tire is produced using the polymer laminate according to the present invention as an inner liner. Since the SIBS, SIS, SIB, epoxidized SBS, and the like constituting the polymer laminate are thermoplastic resins, when heated to, for example, 150 to 180 ° C. in the process of obtaining a vulcanized tire, the polymer laminate is softened. It becomes. Since the thermoplastic resin in the softened state is more reactive than the solid state, it is fused to the adjacent member.

  That is, the inner liner in contact with the outer surface of the expanded bladder is softened by heating and fused to the bladder. If an attempt is made to remove the vulcanized tire from the mold while the inner liner and the outer surface of the bladder are fused, the inner liner peels off from the adjacent insulation or carcass, resulting in an air-in phenomenon. In addition, the tire shape itself may be deformed.

  Therefore, the thermoplastic resin used for the inner liner can be solidified by immediately cooling the obtained vulcanized tire at 120 ° C. or lower for 10 seconds or longer. When the thermoplastic resin is solidified, the fusion between the inner liner and the bladder is eliminated, and the releasability when the vulcanized tire is taken out from the mold is improved.

  The cooling temperature is preferably 50 to 120 ° C. When the cooling temperature is lower than 50 ° C., it is necessary to prepare a special cooling medium, which may deteriorate productivity. When the cooling temperature exceeds 120 ° C., the thermoplastic resin is not sufficiently cooled, and the inner liner remains fused to the bladder when the mold is opened, which may cause an air-in phenomenon. The cooling temperature is more preferably 70 to 100 ° C.

  The cooling time is preferably 10 to 300 seconds. If the cooling time is shorter than 10 seconds, the thermoplastic resin is not sufficiently cooled, and the inner liner remains fused to the bladder when the mold is opened, which may cause an air-in phenomenon. When the cooling time exceeds 300 seconds, the productivity is deteriorated. The cooling time is more preferably 30 to 180 seconds.

  The step of cooling the vulcanized tire is preferably performed by cooling the inside of the bladder. Since the inside of the bladder is hollow, a cooling medium adjusted to the cooling temperature can be introduced into the bladder after the vulcanization process is completed.

  The process of cooling the vulcanized tire can be performed by cooling the inside of the bladder and installing a cooling structure in the mold.

  As the cooling medium, it is preferable to use one or more selected from the group consisting of air, water vapor, water, and oil. Among these, it is preferable to use water that is excellent in cooling efficiency.

<Examples 1 to 15 and Comparative Examples 1 to 12>
(Production of polymer sheet)
Each compounding agent was put into a twin screw extruder (screw diameter: φ50 mm, L / D: 30, cylinder temperature: 220 ° C.) according to the formulation shown in Table 1 and Table 2, and kneaded at 200 rpm to be pelletized. The obtained pellets were put into a T-die extruder (screw diameter: φ80 mm, L / D: 50, die grip width: 500 mm, cylinder temperature: 220 ° C., film gauge: 0.3 mm), and a thickness of 0.3 mm A polymer laminate was prepared.

(Production of pneumatic tires)
The obtained polymer laminate was applied to the inner liner portion of the tire to prepare a raw tire. The green tire was press-molded in a mold at 170 ° C. for 20 minutes to produce a 195 / 65R15 size vulcanized tire.

  Here, in order to adjust the thickness in the bead region Rb and the buttress region Rs of the inner liner, a profile is attached to the extrusion port of the polymer sheet, and an integrated sheet in which the thickness Gs of the buttress region is reduced is prepared. This was disposed on the inner surface of the tire as an inner liner.

<Performance test>
Pneumatic tires were produced using the polymer laminates of the examples and comparative examples as inner liners, and the following performance tests were performed.

<Peel test>
An inner liner (polymer laminate) and a rubber sheet for carcass (components: natural rubber and SBR) were stacked and heated under pressure at 170 ° C. for 12 minutes to prepare a 25 mm-wide strip test piece. The polymer laminate was stacked so that the SIS layer or SIB layer was in contact with the rubber sheet. Using the obtained test piece, in accordance with JIS K 6256 “How to determine the adhesion of vulcanized rubber and thermoplastic rubber”, a peel test is performed at room temperature of 23 ° C., and the peel strength between the inner liner and the carcass is measured. It was measured. The larger the inner liner and carcass peeling force, the better.

<Bending fatigue test>
A predetermined test piece having a groove at the center was prepared in accordance with JIS K 6260 “Demach flex cracking test method for vulcanized rubber and thermoplastic rubber”. As the inner liner, a sheet having a thickness of 0.3 mm was attached to rubber and vulcanized to prepare a predetermined test piece. An incision was made in advance at the center of the groove of the test piece, and a test was conducted in which bending growth was repeatedly applied and crack growth was measured. The crack length was measured at an ambient temperature of 23 ° C., a strain of 30%, and a period of 5 Hz, and the number of repetitions of bending deformation required for the crack to grow by 1 mm was calculated. Using the value of Comparative Example 1 as a reference (100), the bending fatigue properties of the polymer laminates of each Example and each Comparative Example were shown as an index. It can be said that the larger the numerical value, the better the cracks are less likely to grow. For example, the index of Example 1 is obtained by the following formula.

(Bending fatigue index) = (Number of repetitions of bending deformation of Example 1) / (Number of repetitions of bending deformation of Comparative Example 1) × 100
<Static air pressure drop rate test>
The 195 / 65R15 steel radial PC tire manufactured by the above-described method was assembled into a JIS standard rim 15 × 6JJ, sealed with an initial air pressure of 300 kPa, and left at room temperature for 90 days, and the rate of decrease in air pressure was calculated. It can be said that the smaller the decrease in air pressure, the better the air pressure is less likely to decrease.

<Measurement of average thickness>
A 195 / 65R15 steel radial PC tire was divided into 8 equal parts in the circumferential direction, and 8 cut samples cut along the tire radial direction with a width of 20 mm were created at each location, and each of these 8 cut samples was The thickness of the inner liner was measured at five points equally divided into five in the buttress region Rs and the bead region Rb. The arithmetic average values of the total 40 measured values were Gs and Gb.

<Crack resistance>
195 / 65R15 steel radial PC tire is assembled to JIS standard rim 15 × 6JJ, filled with regular air pressure, and the maximum load corresponding to this air pressure is applied from the air pressure-addition capacity correspondence table with JATMA YEAR BOOK, speed 80km / The vehicle traveled on the drum at h, and when the damage that could be visually confirmed was generated, the vehicle was stopped and the travel distance was determined. The travel distance of Comparative Example 1 is taken as 100 and is shown as an index. The larger the index, the better the crack resistance.

(Evaluation results)
The test results are shown in Tables 1 and 2.

(Note 1) SIBS: “Sibstar SIBSTAR 102T” manufactured by Kaneka Corporation (Shore A hardness 25, styrene content 25% by mass).
(Note 2) Polyamide polymer: “UBESTA XPA 90” manufactured by Ube Industries, Ltd.
40 (Shore D hardness 40) ".
(Note 3) Ethylene-vinyl alcohol copolymer: “Eval E105” manufactured by Kuraray Co., Ltd.
(Note 4) Chlorobutyl: “Exon Chlorobutyl 1068” manufactured by ExxonMobil Corporation.
(Note 5) NR (natural rubber): TSR20.
(Note 6) Filler: “Seast V” manufactured by Tokai Carbon Co., Ltd. (N660, N ₂ SA: 2)
7 m ² / g).
(Note 7) Organized clay mineral: “BENTONE 34” manufactured by Pheox (layered clay mineral: hectorite viscosity mineral, organic compound: dimethyl distearyl ammonium salt, cation exchange amount of organic compound: 100 meg / 100 g).
(Note 8) Inorganic clay mineral: “Kunipia F” from Kunimine Industry Co., Ltd.
(Note 9) SIS: styrene-isoprene-styrene block copolymer, “D1161JP” manufactured by Kraton Polymer Co., Ltd. (styrene content: 15%).
(Note 10) SIB: Styrene-isobutylene diblock copolymer (produced by the production method described in the following (Production of SIB)).

(Manufacture of SIB)
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. The 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.

(Consideration of evaluation results)
The pneumatic tires of Examples 1 to 3 and Comparative Example 5 were the same except that the mass parts of the organically treated viscosity mineral contained in the inner liner were changed. The pneumatic tires of Examples 1 to 3 are excellent in air permeability resistance, bending fatigue resistance, and crack resistance because the inner liner contains 0.1 to 50 parts by mass of the organically treated viscosity mineral. It was a thing. On the other hand, in the pneumatic tire of Comparative Example 5, since the inner liner contains more than 50 parts by mass of the organically treated viscosity mineral, the air permeation resistance is equal to that of the pneumatic tires of Examples 1 to 3. However, the bending fatigue resistance and crack resistance were remarkably low.

  Example 4 is the same as Example 2 except that 20% by mass of SIBS contained in the inner liner was replaced with an ethylene-vinyl alcohol copolymer with respect to the pneumatic tire of Example 2. did. From the results of the performance of the pneumatic tire of Example 4, it is clear that even if a part of SIBS is replaced with an ethylene-vinyl alcohol copolymer, the performance equivalent to that of the pneumatic tire of Example 1 can be obtained. It was.

  In the pneumatic tires of Examples 5 to 7 and Comparative Example 3, the average thickness Gb of the bead region Rb of the inner liner and the average thickness Gs of the buttress region Rs extending from the tire maximum width position to the corresponding position Lu of the belt layer end. The ratio was the same except that the ratio (Gb / Gs) was different.

  That is, in the pneumatic tires of Examples 5 to 7, the average thickness Gb of the bead area Rb extending from the tire maximum width position to the bead toe is the average of the buttress area Rs extending from the tire maximum width position to the corresponding position Lu of the belt layer end. Since the thickness Gs was thin, it was excellent in air permeation resistance, bending fatigue resistance, and crack resistance. On the other hand, in the pneumatic tire of Comparative Example 3, the average thickness Gb of the bead region Rb extending from the tire maximum width position to the bead toe and the average thickness of the buttress region Rs extending from the tire maximum width position to the corresponding position Lu of the belt layer end. Since Gs is the same, all of the air permeation resistance, the bending fatigue resistance, and the crack resistance were insufficient as compared with the pneumatic tires of Examples 5 to 7.

  In the pneumatic tires of Examples 8 to 11 and Comparative Example 11, the average thickness Gb of the bead region Rb of the inner liner and the average thickness Gs of the buttress region Rs extending from the tire maximum width position to the corresponding position Lu of the belt layer end. The ratio was the same except that the ratio (Gb / Gs) was different.

  That is, in the pneumatic tires of Examples 8 to 11, the average thickness Gb of the bead region Rb extending from the tire maximum width position to the bead toe is the average of the buttress region Rs extending from the tire maximum width position to the corresponding position Lu of the belt layer end. Since the thickness Gs was thin, it was excellent in air permeation resistance, bending fatigue resistance, and crack resistance. On the other hand, in the pneumatic tire of Comparative Example 11, the average thickness Gb of the bead region Rb extending from the tire maximum width position to the bead toe and the average thickness of the buttress region Rs extending from the tire maximum width position to the corresponding position Lu of the belt layer end. Since Gs is the same, all of the air permeation resistance, the bending fatigue resistance, and the crack resistance were insufficient as compared with the pneumatic tires of Examples 8 to 11.

  In the pneumatic tires of Examples 12 to 15 and Comparative Example 12, the average thickness Gb of the bead region Rb of the inner liner and the average thickness Gs of the buttress region Rs extending from the tire maximum width position to the corresponding position Lu of the belt layer end. The ratio was the same except that the ratio (Gb / Gs) was different.

  That is, in the pneumatic tires of Examples 12 to 15, the average thickness Gb of the bead area Rb extending from the tire maximum width position to the bead toe, and the average of the buttress area Rs extending from the tire maximum width position to the corresponding position Lu of the belt layer end. Since the thickness Gs was thin, it was excellent in air permeation resistance, bending fatigue resistance, and crack resistance. On the other hand, in the pneumatic tire of Comparative Example 12, the average thickness Gb of the bead region Rb extending from the tire maximum width position to the bead toe and the average thickness of the buttress region Rs extending from the tire maximum width position to the corresponding position Lu of the belt layer end. Since Gs was the same, all of the air permeation resistance, the bending fatigue resistance, and the crack resistance were insufficient as compared with the pneumatic tires of Examples 12 to 15.

  On the other hand, since the pneumatic tires of Comparative Examples 1, 9, and 10 do not contain SIBS in the first layer, compared with the pneumatic tires of Examples 1 to 15, the air permeation resistance and the flex fatigue resistance Both the crack resistance and the crack resistance were insufficient.

  The pneumatic tires of Comparative Examples 4 and 6 have the same air permeation resistance as the pneumatic tires of Examples 1 to 15 because the inner liner does not contain an organically treated viscosity mineral. The fatigue and crack resistance was remarkably low.

  In the pneumatic tires of Comparative Examples 7, 9, and 10, the inner liner contains less than 60 parts by mass of SIBS. Therefore, compared to the pneumatic tires of Examples 1 to 15, the air permeation resistance, the bending fatigue resistance, Both the crack resistance and the crack resistance were insufficient.

  Since the inner tire of the pneumatic tire of Comparative Example 8 does not contain a polyamide-based polymer, compared to the pneumatic tires of Examples 1 to 15, the air permeation resistance, the bending fatigue resistance, and the crack resistance None of these performances were insufficient.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  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, 10 polymer laminated body, 11 1st layer, 12 SIS layer , 13 SIB layer, Rb bead area, Rs buttress area, Le tire maximum width position, Lt bead toe, Lu belt layer corresponding position.

Claims (6)

A pneumatic tire with an inner liner on the inside of the tire,
The inner liner is 100 mass% of a polymer mixture containing 99-60 mass% of a styrene-isobutylene-styrene triblock copolymer and 1-40 mass% of a polyamide-based polymer having a Shore D hardness of 70 or less containing polyamide in the molecular chain. A first layer having a thickness of 0.05 to 0.6 mm, a styrene-isoprene-styrene triblock copolymer, and styrene. A polymer laminate comprising at least one of isobutylene diblock copolymers and comprising a second layer having a thickness of 0.01 to 0.3 mm;
The second layer is disposed in contact with the rubber layer of the carcass ply;
The inner liner is characterized in that the average thickness Gs of the buttress region Rs from the tire maximum width position to the corresponding position Lu of the belt layer end is thinner than the average thickness Gb of the bead region Rb extending from the tire maximum width position to the bead toe. And pneumatic tires.   2. The pneumatic tire according to claim 1, wherein a ratio (Gs / Gb) of an average thickness Gs of the buttress region of the inner liner to an average thickness Gb of the bead region is 0.3 to 0.75.   The pneumatic tire according to claim 1 or 2, wherein an average thickness Gs of a buttress region of the inner liner is 0.05 to 0.45 mm.   The pneumatic tire according to any one of claims 1 to 3, wherein the polymer mixture includes 15 to 40% by mass of an ethylene-vinyl alcohol copolymer.   The pneumatic tire according to any one of claims 1 to 4, wherein the styrene-isobutylene-styrene triblock copolymer contains 10 to 30% by mass of styrene.   The pneumatic tire according to any one of claims 1 to 5, wherein the polyamide-based polymer is a block copolymer including a polyamide component and a polyether component.

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