JP5143958B1 - Pneumatic tire - Google Patents

Abstract

An object of the present invention is to suppress bending crack growth of a pneumatic tire and improve weather resistance, air permeation resistance and rolling resistance.
An inner liner is composed of a first layer inside a tire and a second layer in contact with a carcass ply. (A) The first layer comprises a styrene-isobutylene-styrene block copolymer and a styrene-isobutylene. -A thermoplastic elastomer, an ultraviolet absorber and an antioxidant containing either a SIBS-modified copolymer in which the styrene block portion of the styrene block copolymer is modified with an acid chloride or acid anhydride having an unsaturated bond. And (B) the second layer contains any of a styrene-isoprene-styrene block copolymer and a styrene-isobutylene block copolymer, and contains a total of 0.5% by mass of an ultraviolet absorber and an antioxidant. 40% by mass and the average thickness Gs of the buttress region Rs is thinner than the average thickness Gb of the bead region Rb. The features.
[Selection] Figure 1

Description

  The present invention relates to a pneumatic tire provided with an inner liner, and more particularly, to a pneumatic tire that suppresses the growth of bent cracks in the inner liner due to repeated bending deformation during running of the tire and has improved air permeability and weather resistance.

  In recent years, tires have been made lighter due to the strong social demand for lower fuel consumption of vehicles, and inner liners that require air permeation resistance among tire members are also being made lighter. It has become.

  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. Yes. 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 is superior in air permeation resistance to 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, it is exposed to the outdoors during tire transportation and during display at dealers, and is subject to deterioration by the ultraviolet rays of sunlight, giving the impression that the thermoplastic elastomer deteriorates and the inside cracks are poor. Since pneumatic tires are filled with air during use, oxygen in the air penetrates into the tire components and oxidation progresses over time, which adversely affects the durability of pneumatic tires. Will be affected. In particular, when a crack occurs in the inner liner, it gives the user an impression that the inside appearance is bad. Further, the gas barrier property is partially deteriorated and the tire internal pressure is lowered.

  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. Is known.

  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. The large number of small spots on the inside of the tire gives the user an impression that the appearance is poor, and air is the starting point during running, causing separation, cracking the inner liner, and reducing the tire internal pressure.

  In Patent Document 1, titanium oxide is blended with a blend of butyl rubber and nylon resin to prevent ultraviolet deterioration. However, in addition to UV degradation, there is a problem that durability deteriorates due to degradation due to generation of radicals in nylon resin due to bending fatigue.

  In Patent Document 2, a light-shielding layer in which carbon black is blended as a release agent is provided on the surface layer in order to prevent ultraviolet degradation of the thermoplastic elastomer layer. However, due to variations in the process of applying as a mold release agent, it cannot be applied uniformly on the inner surface of the tire, or if it is scratched by the operator's or user's hand in the process or other causes, it will not function as a light shielding layer and will deteriorate UV rays As a result, there is a problem that durability is lowered.

  In Patent Document 3, the low temperature durability is improved by designing the thickness at the shoulder portion to be larger than the thickness at the tire crown portion, but the thickness at the shoulder portion is designed to be thicker than the tire crown portion. This suppresses bending deformation and reduces the occurrence of cracks, but is disadvantageous in terms of reducing the weight of the tire.

JP 2009-298986 A International Publication No. 2007/116983 JP 2005-343379 A

  The present invention, in a pneumatic tire equipped with an inner liner, suppresses bending crack growth of the inner liner due to repeated bending deformation during running of the tire, and comprehensively improves weather resistance, air permeation resistance and rolling resistance. It is to be.

The present invention is a pneumatic tire in which a carcass layer extending from the tread portion to the right and left bead portions, a belt layer outside the crown portion, and an inner liner inside the carcass layer,
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,
(A) The first layer is a SIBS in which a styrene block portion of a styrene-isobutylene-styrene block copolymer and a styrene-isobutylene-styrene block copolymer is modified with an acid chloride or acid anhydride having an unsaturated bond. An elastomer composition comprising a thermoplastic elastomer containing at least one of a modified copolymer, an ultraviolet absorber and an antioxidant,
(B) The second layer includes an elastomer containing at least one of a styrene-isoprene-styrene block copolymer and a styrene-isobutylene block copolymer,
The first layer and the second layer are an elastomer composition containing an ultraviolet absorber and an antioxidant in a total amount of 0.5% to 40% by weight of the elastomer component,
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. It relates to a pneumatic tire.

  The total amount of the ultraviolet absorber and the antioxidant in the first layer and the second layer is preferably 0.5% by mass to 40% by mass of the elastomer component.

  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 0.5 to 0.7.

  The average thickness Gs of the buttress area of the inner liner is preferably 0.06 to 0.30 mm.

  Furthermore, the elastomer composition of any one of the first layer and the second layer preferably contains 5% by mass to 100% by mass of an SIBS-modified copolymer.

  The elastomer composition of any one of the first layer and the second layer preferably contains a tackifier or polyisobutylene.

  In the present invention, the ratio of the average thickness Gs of the buttress region Rs of the inner liner to the average thickness Gb of the bead region Rb (Gs / Gb) is made smaller than 1, so that the stress in the buttress region due to bending deformation is effectively reduced. The structure is relaxed. And the thermoplastic elastomer composition containing a styrene-isobutylene-styrene block copolymer (SIBS) is used for the inner liner. Here, the composition containing SIBS or the like is susceptible to deterioration in the wavelength region of 290 nm or more of ultraviolet light. Therefore, by blending an ultraviolet absorber into the thermoplastic elastomer composition, it absorbs the light of 320 nm to 350 nm, which is most susceptible to degradation, and converts it into vibrational energy or thermal energy of the molecule, thereby converting the thermoplastic elastomer from ultraviolet rays. Has a function to protect. Here, the ultraviolet absorber includes a light stabilizer.

  Thermoplastic elastomers generate radicals due to bending fatigue during tire running, and the radicals induce chain degradation of the main chain, leading to cracks and breakage of the inner liner made of the thermoplastic elastomer composition. . Therefore, by adding an antioxidant, it acts to trap radicals generated by bending fatigue and prevent deterioration. Here, the antioxidant includes an oxygen absorbent.

It is a schematic sectional drawing of the right half of the pneumatic tire of this invention. It is a schematic sectional drawing which shows the joining state of an inner liner and a carcass.

  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 °. 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.

  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 less than 1, preferably 0. .5 to 0.7. In order to maintain the air pressure holding performance and to relieve the stress in the buttress area, the average thickness Gs of the buttress area Rs of the inner liner is preferably 0.05 to 0.40 mm.

<Inner liner>
The present invention is a pneumatic tire provided with an inner liner on the inner side of the tire, and the inner liner is formed of at least two polymer laminates. The first layer is an elastomer composition based on styrene-isobutylene-styrene triblock copolymer (SIBS), and the second layer is styrene-isoprene-styrene triblock copolymer (SIS) and styrene-isobutylene. It is an elastomer composition mainly comprising at least one of a diblock copolymer (SIB).
As an elastomer component of the first layer and the second layer, a styrene-isobutylene-styrene block copolymer in which the styrene block portion of SIBS is modified with an acid chloride or acid anhydride having an unsaturated bond (hereinafter referred to as “SIBS-modified copolymer”). Also referred to as a "polymer"). The elastomer composition of the first layer and the second layer contains an ultraviolet absorber and an antioxidant.

<Elastomer component of the first layer>
In the present invention, the first layer contains a styrene-isobutylene-styrene block copolymer (hereinafter also referred to as “SIBS”) as an elastomer component. Since SIBS contains an isobutylene block in the molecular chain, the polymer film has excellent air permeation resistance. Therefore, when SIBS is used for the inner liner, a pneumatic tire excellent in air permeation resistance can be obtained. Furthermore, since SIBS is saturated in its molecular structure except for aromatic units, oxidative degradation is suppressed.

  The molecular weight of SIBS is preferably 50,000 to 400,000 in terms of weight average molecular weight by GPC measurement from the viewpoints of fluidity, molding process and rubber elasticity. 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 making the air permeation resistance and durability better, SIBS preferably has a styrene component content in SIBS of 10 to 30% by mass.

  In SIBS, the degree of polymerization of each block in the molecular chain is preferably about 10,000 to 150,000 for isobutylene units and about 5,000 to 30,000 for styrene units. SIBS can be produced by a living cationic polymerization method of a general vinyl compound. For example, JP-A-62-48704 and JP-A-64-62308 disclose living cationic polymerization of isobutylene and other vinyl compounds.

<Elastomer component of the second layer>
The second layer is an elastomer containing at least one of a styrene-isoprene-styrene block copolymer (hereinafter also referred to as “SIS”) and a styrene-isobutylene block copolymer (hereinafter also referred to as “SIB”). It is a composition.

  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.

  The molecular weight of the 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. 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 about 300 to 3,000 for isobutylene and 10 to 1,50 for styrene from the viewpoint of rubber elasticity and handling.
It is preferably about zero.

  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. Thereafter, a large amount of methanol is added to stop the reaction, followed by vacuum drying at 60 ° C. to obtain SIB.

(Mixed with SIBS)
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 mixed is adjusted in the range of 10 to 80% by mass of the thermoplastic 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.

<Elastomer component of first layer and second layer>
(SIBS-modified copolymer)
The elastomer composition of the first layer may include 10% by mass to 100% by mass of the elastomer component of the SIBS-modified copolymer. The elastomer composition of the second layer contains the SIBS-modified copolymer in the range of 5 to 80% by mass, preferably 10 to 80% by mass of the elastomer component. When the SIBS-modified copolymer is less than 5% by mass, the vulcanization adhesive force between the first layer and the second layer or between the second layer and the carcass ply may be reduced. If it exceeds, the adhesive strength with the carcass ply may be reduced.

  Here, the SIBS-modified copolymer is a styrene-isobutylene-styrene block copolymer (SIBS) in which the styrene block portion is modified with an acid chloride or acid anhydride having an unsaturated bond, and in the molecular chain. The chemical structure of the following formula (1) is included.

In the formula (1), n is an integer, and R1 is a monovalent organic group having a functional group.
The acid chloride having an unsaturated bond used for modification in the present invention includes methacrylic acid chloride, methacrylic acid bromide, methacrylic acid iodide, acrylic acid chloride, acrylic acid bromide, acrylic acid iodide, crotonyl acid chloride and crotonyl acid bromide. Illustrated. In particular, methacrylic acid chloride and acrylic acid chloride are suitable. Examples of the acid anhydride include acetic anhydride, maleic anhydride, and phthalic anhydride, and acetic anhydride is particularly preferable. Such modification introduces an unsaturated group into SIBS, so that the molecular chain can be crosslinked with a crosslinking agent.

  As described above, the blending amount of the SIBS-modified copolymer obtained by modifying the styrene-isobutylene-styrene block copolymer with an acid chloride and an acid anhydride having an unsaturated bond is 10 to 100 mass of the thermoplastic elastomer component. %, Preferably in the range of 30 to 100% by mass. When the blending amount of the SIBS-modified copolymer is less than 10% by mass of the thermoplastic elastomer component, vulcanization adhesion between the second layer and the carcass ply rubber may not be sufficient.

  The content of acid chloride and acid anhydride having an unsaturated bond in the SIBS-modified copolymer is 1% by weight or more, preferably 5% by weight or more, and 30% by weight or less.

  The SIBS-modified copolymer can be subjected to thermal crosslinking and crosslinking with a crosslinking agent by conventional methods.

  Since the SIBS-modified copolymer is derived from the isobutylene block, the film made of the SIBS-modified copolymer has excellent air permeation resistance. In addition, since the unsaturated group is introduced into ISBS, the SIBS-modified copolymer can be crosslinked by thermal crosslinking and a crosslinking agent, and has basic properties such as tensile strength, elongation at break and permanent strain, as well as flex crack properties and The air permeation resistance is improved and the properties as an inner liner are improved.

  The molecular weight of the SIBS-modified copolymer is not particularly limited, but the weight average molecular weight by GPC measurement is preferably 50,000 to 400,000 from the viewpoint 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 the air permeation resistance and durability of the SIBS-modified copolymer, the content of the styrene component in SIBS is preferably 10 to 30% by mass, and preferably 14 to 23% by mass.

  The SIBS is a copolymer in which the degree of polymerization of each block is about 10,000 to 150,000 for isobutylene from the viewpoint of rubber elasticity and handling (becomes liquid when the degree of polymerization is less than 10,000), and styrene. Then, it is preferable that it is about 5,000-30,000.

  As a method for producing the SIBS-modified copolymer, for example, the following method can be adopted. After placing the styrene-isobutylene-styrene block copolymer in a separable flask, the inside of the polymerization vessel is purged with nitrogen. Thereafter, an organic solvent (for example, n-hexane and butyl chloride) dried with molecular sieves is added, and methacrylic acid chloride is further added. Finally, aluminum trichloride is added and reacted while stirring the solution. After a certain time from the start of the reaction, a predetermined amount of water is added to the reaction solution and stirred to terminate the reaction. The reaction solution is washed with a large amount of water several times or more, further slowly dropped into a large amount of methanol and acetone mixed solvent to precipitate a polymer, and the obtained polymer is vacuum dried. A method for producing a SIBS-modified copolymer is disclosed in, for example, Japanese Patent No. 4551005.

(Styrenic thermoplastic elastomer)
The first layer and the second layer can include a styrenic thermoplastic elastomer. Here, the styrene thermoplastic elastomer refers to a copolymer containing a styrene block as a hard segment. In addition to the SIBS, SIS, SIB, styrene-butadiene-styrene block copolymer (SBS), styrene-isobutylene-styrene block copolymer (SIBS), styrene-ethylene-butene-styrene block copolymer (SEBS), There are styrene-ethylene / propylene / styrene block copolymer (SEPS), styrene / ethylene / ethylene / propylene / styrene block copolymer (SEEPS), and styrene / butadiene / butylene / styrene block copolymer (SBBS).

  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.

(Rubber component)
A rubber component can be mix | blended with the thermoplastic elastomer composition of a 1st layer. By blending 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 amount of the rubber component is preferably in the range of 5 to 75% by mass of the elastomer component.

<Ultraviolet absorber>
In the present invention, the elastomer composition contains a UV absorber. The ultraviolet absorber absorbs light in the ultraviolet region having a wavelength of 290 nm or more, and prevents deterioration of the molecular chain of the polymer compound. For example, benzophenone-based, salicylate-based, and benzotriazole-based ultraviolet absorbers absorb ultraviolet light having a wavelength of about 320 nm to about 350 nm, in which a polymer compound is most susceptible to deterioration. It has a function of preventing absorption into a polymer compound by converting light in this wavelength range into vibration energy or heat energy. In particular, benzotriazole ultraviolet absorbers can absorb a wide range of ultraviolet light. Here, an example of the ultraviolet absorber is as follows.

[Benzotriazole UV absorber]
TINUVIN P / FL (BASF, molecular weight 225, melting point 128-132 ° C, maximum absorption wavelength 341 nm) (2- (2-hydroxy-benzotriazol-2-yl) -p-cresol), TINUVIN 234 (BASF) , Molecular weight 447.6, melting point 137-141 ° C., maximum absorption wavelength 343 nm) (2- [2-hydroxy-3,5-bis (α, α′dimethylbenzyl) phenyl] -2H-benzotriazole), TINUVIN 326 / FL (manufactured by BASF, molecular weight 315.8, melting point 138 to 141 ° C., maximum absorption wavelength 353 nm), ADK STAB LA-36 (manufactured by ADEKA) (2- (2′-hydroxy-3′-tert-butyl-) 5′-methylphenyl) -5-chlorobenzotriazole), TINUVIN 237 (manufactured by BASF, molecular weight 338.4, melting point 139-144 ° C., maximum absorption wavelength 359 nm) (2,4-di-t-butyl) -6- (5-chlorobenzotriazol-2-yl-) phenol), TINUVIN 328 (manufactured by BASF, molecular weight 351.5, melting point 80-88 ° C., maximum absorption wavelength 347 nm) (2- (3,5-di -T-amyl-2-hydroxyphenyl) benzotriazole), TINUVIN 329 / FL (manufactured by BASF, molecular weight 323, melting point 103-105 ° C., maximum absorption wavelength 343 nm) (2- (2-hydroxy-benzotriazole-2- Yl) -4-tert-octylphenol).

[Liquid UV absorber]
TINUVIN 213 (manufactured by BASF, melting point −40 ° C., maximum absorption wavelength 344 nm) (methyl 5- (2-hydroxy-benzotriazol-2-yl) -4-hydroxy-3-tert-butylbenzenepropanoate), TINUVIN 571 (BASF, molecular weight 393.6, melting point −56 ° C., maximum absorption wavelength 343 nm) (2- (2-hydroxy-benzotriazol-2-yl) -4-methyl-6-dodecylphenol).

[Triazine UV absorber]
TINUVIN 1577FF (manufactured by BASF, molecular weight 425, melting point 148 ° C., maximum absorption wavelength 274 nm) (2- [4,6-diphenyl-1,3,5-triazin-2-yl] -5- (hexyloxy) phenol) .

[Benzophenone UV absorber]
CHIMASSORB 81 / FL (BASF, molecular weight 326.4, melting point 48-49 ° C.) (2-hydroxy-4- (octyloxy) benzophenone).

[Benzoate UV absorber]
TINUVIN 120 (BASF, molecular weight 438.7, melting point 192 to 197 ° C., maximum absorption wavelength 265 nm) (2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate) .

[Hindered amine stabilizer]
CHIMASSORB 2020 FDL (BASF, molecular weight 2600-3400, melting point 130-136 ° C.) (dibutylamine 1,3,5-triazine / N, N-bis (2,2,6,6-tetramethyl-4-piperidyl) -1,6-hexamethylenediamine · N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate), CHIMASSORB 944 FDL (BASF, molecular weight 2000-3100, melting point 100- 135 ° C) (poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl -4-piperidyl) imino} hexamethylene {2,2,6,6-tetramethyl-4-piperidyl) imino}]), TINUVIN 622 LD (BASF, molecular weight 3100-4000, melting point 55-70 ° C.) Butanedioic acid 1- 2- (4-hydroxy-2,2,6,6-tetramethylpiperidino) ethyl]), TINUVIN 144 (manufactured by BASF, molecular weight 685, melting point 146-150 ° C.) (2-butyl-2- [3 , 5-di (tert-butyl) -4-hydroxybenzyl] malonate bis (1,2,2,6,6-pentamethyl-4-piperidyl), TINUVIN 292 (BASF, molecular weight 509) (bis sebacate) (1,2,2,6,6-pentamethyl-4-piperidinyl)), TINUVIN 770 DF (manufactured by BASF, molecular weight 481, melting point 81-85 ° C.) (bis (2,2,6,6-tetra sebacate)) Methylpiperidin-4-yl).

<Antioxidant>
In the present invention, the elastomer composition contains an antioxidant. As for the antioxidant, the ultraviolet absorber functions as a radical scavenger, and mainly by capturing carbon radicals, it is possible to prevent deterioration of the molecular chain of the polymer. The antioxidant is exemplified below.

[Hindered phenolic antioxidants]
IRGANOX 1010 (manufactured by BASF), Adeka Stub AO-60 (manufactured by ADEKA), Sumilyzer BP-101 (manufactured by Sumitomo Chemical Co., Ltd.) (pentaerythrityl tetrakis [3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate]), IRGANOX 1035 (BASF) (2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]), IRGANOX 1076 (BASF) ) (Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate), IRGANOX 1098 (manufactured by BASF) (N, N′-hexamethylenebis (3,5-di-t-butyl- 4-hydroxy-hydrocinnamamide)), IRGANOX1135 (manufactured by BASF) (isooctyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]), IRGANOX1330 BASF) (1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene), IRGANOX 1726 (BASF) (4,6-bis ( Dodecylthiomethyl) -O-cresol), IRGANOX 1425 (manufactured by BASF) (bis (3,5-di-t-butyl-4-hydroxybenzylphosphonate ethyl) calcium (50%), polyethylene wax (50%)), IRGANOX1520 (manufactured by BASF) (2,4-bis [(octylthio) methyl] -O-cresol), IRGANOX245 (manufactured by BASF) (triethyleneglycol-bis [3- (3-t-butyl-5-methyl-4- Hydroxyphenyl) propionate]), IRGANOX259 (BASF) (1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]), IRGANOX3114 (BASF (Tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate), IRGANOX5057 (manufactured by BASF) (octylated diphenylamine), IRGANOX565 (manufactured by BASF) (2,4-bis- (N-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine), Sianox CY1790 (manufactured by Sun Chemical Co., Ltd.) (1,3,5 -Tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid), ADK STAB AO-40 (manufactured by ADEKA), Sumilycer BBM (manufactured by Sumitomo Chemical Co., Ltd.) (4,4 '-Butylidenebis (3-methyl-6-t-butylphenol)), ADK STAB AO-50 (manufactured by ADEKA), Sumilizer BP-76 (manufactured by Sumitomo Chemical Co., Ltd.) (stearyl-β- (3,5- G -Butyl-4-hydroxyphenyl) propionate), ADK STAB AO-80 (manufactured by ADEKA Corporation), Sumilyzer GA-80 (manufactured by Sumitomo Chemical Co., Ltd.) (3,9-bis [1,1-dimethyl-2-one) [Β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [5,5] -undecane).

[Phosphorus antioxidant]
The phosphorus-based antioxidant is used as a peroxide decomposing agent and has an excellent antioxidant function at the time of thermal processing molding, and the following can be exemplified.

  IRGAFOS12 (BASF, molecular weight 1462.9) (6,6 ′, 6 ″-[nitrilotris (ethyleneoxy)] tris (2,4,8,10-tetra-tert-butylbenzo [d, f] [1 , 3,2] dioxaphosphepine)), IRGAFOS38 (BASF, molecular weight 514) (ethylbisphosphite (2,4-di-tert-butyl-6-methylphenyl)), IRGAFOS168 (BASF, molecular weight) 646), ADK STAB 2112 (manufactured by ADEKA), Sumilyzer P-16 (manufactured by Sumitomo Chemical Co., Ltd.) (Tris (2,4-di-t-butylphenyl) phosphite), ADK STAB PEP-8 ((Strain) ADEKA) (distearyl pentaerythritol diphosphite), ADK STAB PEP-36 (manufactured by ADEKA) (cyclic neopentanetetraylbis (2,6-di-t-butyl-) 4-methylphenyl) phosphite).

[Hydroxylamine type]
IRGASTAB FS 042 (manufactured by BASF) (N, N-dioctadecylhydroxylamine).

[Hindered phenol / phosphorus mixed antioxidant]
IRGANOX B 225 (BASF) (IRGAFOS168: IRGANOX1010 = 1: 1), IRGANOX215 (BASF) (IRGAFOS168: IRGANOX1010 = 2: 1), IRGANOX220 (BASF) (IRGAFOS168: IRGANOX1010 = 3: 1), IRGANOX921 (BASF (Made by IRGAFOS168: IRGANOX1076 = 2: 1).

[Oxygen absorber]
In the present invention, the antioxidant is a concept including an oxygen absorbent. As the oxygen absorbent, a general oxygen absorbent capable of scavenging oxygen in the air can be used, for example, an iron powder oxygen absorbent that absorbs oxygen in the air by utilizing an oxidation reaction of iron powder. Usually, 0.1 to 50 parts by weight of a metal halide such as sodium chloride, sodium bromide, calcium chloride, magnesium chloride, etc. per 100 parts by weight of iron powder having a surface area of 0.5 m ² / g or more. A combination of alkali metal or alkaline earth metal halides such as chlorine, bromine and iodine is used. This may be a mixture of both, or the iron powder surface coated with a metal halide. The oxygen absorbent used in the present invention can be further combined with a porous particle such as zeolite impregnated with water to further promote the oxidation of iron by oxygen. In particular, a hindered phenol-based antioxidant is preferred as a radical trapping agent for carbon radicals.

  In this invention, about the said ultraviolet absorber and antioxidant, at least 1 sort (s) or 2 or more types can be used in combination. In particular, it is preferable to use a combination of a benzotriazole ultraviolet absorber and a hindered phenol antioxidant.

<Tackifier>
In the present invention, at least one of the first layer and the second layer has a tackifier in the range of 0.1 to 100 parts by weight, preferably 1.0 to 20 parts by weight with respect to 100 parts by weight of the thermoplastic elastomer component. It is blended with. Here, the tackifier refers to a compounding agent for enhancing the tackiness of the elastomer composition, and examples thereof include the following tackifiers.

  This is because in the case of the first layer, it is necessary to increase the vulcanization adhesive strength with the second layer and to maintain processability, productivity and gas barrier properties. On the other hand, in the case of the second layer, it is disposed between the first layer and the carcass ply, thereby improving the adhesion between them and maintaining workability, productivity and gas barrier properties.

  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.

<Inner liner>
(Polymer laminate)
In the present invention, a polymer laminate composed of the first layer and the second layer is used as the inner liner. Here, the first layer and the second layer are elastomer compositions containing a thermoplastic elastomer, 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 composition, adhesion to adjacent members, and fusion, it is preferable to provide a cooling step when manufacturing the tire. In the cooling step, after the tire vulcanization, the inside of the bladder can be cooled by quenching to 50 to 120 ° C. for 10 to 300 seconds. As the cooling medium, at least one selected from air, water vapor, water and oil is used. By adopting such a cooling process, the inner liner can be formed thin.

(Thickness of the first layer and the second layer)
The thickness (Gs) of the inner liner in the buttress region Rs shown in FIG. 1 is preferably as thin as possible within a range that does not impair air permeation resistance, and is preferably set in the range of 0.05 to 0.3 mm.

  The average thickness of the entire first layer is preferably 0.05 to 0.3 mm. When the average thickness of the first layer is less than 0.05 mm, the first layer is broken by the press pressure during vulcanization of the raw tire in which the polymer laminate composed of the first layer and the second layer is applied to the inner liner. Therefore, there is a possibility that an air leak phenomenon may occur in the obtained tire. On the other hand, if the average thickness of the first layer exceeds 0.3 mm, the tire weight increases and the fuel efficiency performance decreases. The average thickness of the first layer is more preferably 0.05 to 0.15 mm. By adjusting the average thickness of the first layer to the above range, it is possible to improve the bending durability of the buttress region while maintaining the air permeation resistance.

  The average thickness of the second layer is preferably 0.01 mm to 0.3 mm. When the average thickness of the second layer is less than 0.01 mm, the second layer is torn by the pressing pressure during vulcanization of the green tire in which the polymer laminate is applied to the inner liner, and the vulcanization adhesion force is reduced. There is a fear. On the other hand, if the average 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 0.15 mm.

  Next, FIG. 2 shows an arrangement state of the inner liner with the carcass ply in the vulcanized tire. In FIG. 2, the polymer laminate PL is composed of a first layer PL1 and a second layer PL2. When the polymer laminate PL is applied to the inner liner of a pneumatic tire, if the second layer PL2 is installed facing the outer side in the tire radial direction so as to be in contact with the carcass ply 6, the second layer PL2 is used in the tire vulcanization process. And the adhesion strength between the carcass 6 can be increased. The obtained pneumatic tire has excellent air permeation resistance and durability because the inner liner and the carcass ply 6 are well bonded.

<Pneumatic tire manufacturing method>
A general manufacturing method can be used for the pneumatic tire of the present invention. First, 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 disposed on the green tire, the second layer PL2 is disposed outward in the tire radial direction so as to be in contact with the carcass ply 6.

<Polymer laminate>
The thermoplastic elastomer (SIB, SIBS, SIS and SIBS-modified copolymer), UV absorber and antioxidant used for the production of the polymer laminate comprising the first layer and the second layer of the present invention were adjusted as follows. .

[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. 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).

[SIBS]
“Sibstar SIBSTAR 102T (Shore A hardness 25, styrene component content 15 mass%, weight average molecular weight: 100,000)” manufactured by Kaneka Corporation was used.

[SIS]
D1161JP (styrene component content 15 mass%, weight average molecular weight: 150,000) manufactured by Kraton Polymer Co., Ltd. was used.

[Production of SIBS-modified copolymer]
In a 2 liter separable flask, 75 g of a styrene-isobutylene block copolymer (styrene content 30%, number of moles of styrene unit 0.216 mol) was placed, and the inside of the container was replaced with nitrogen. Using a syringe, 1200 mL of n-hexane dried with molecular sieves and 1800 ml of n-butyl chloride dried with molecular sieves were added.

Next, 30 g (0.291 mol) of methacrylic acid chloride was added using a syringe. Then, while stirring the solution, 39.4 g (0.295 mol) of aluminum trichloride was added to initiate the reaction. After 30 minutes of reaction, about 1000 milliliters of water was added to the reaction solution and stirred vigorously to complete the reaction. The reaction solution is washed several times with a large amount of water, and further slowly added dropwise to a large amount of methanol / acetone mixed solvent (1: 1) to precipitate the reaction product, and then the reaction product is vacuumed at 60 ° C. for 24 hours. By drying, an SIBS-modified copolymer (weight average molecular weight: 150,000, styrene content: 20% by weight, acid chloride: 1.0% by weight) was obtained.

[Ultraviolet absorber]
“ADEKA STAB LA-36” (2- (2′-hydroxy-3′-ter-butyl-5′-methylphenyl) -5-chlorobenzotriazole) as a benzotriazole ultraviolet absorber manufactured by ADEKA Corporation Using. This ultraviolet absorber has a melting point of 138 to 141 ° C., a molecular weight of 315.8, and a maximum absorption wavelength of 353 nm.

[Antioxidant]
“IRGANOX 1010” (pentaerythrityl tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) was used as a hindered phenol antioxidant manufactured by BASF AG. The melting point of the agent is 110 to 125 ° C., the specific gravity is 1.15, and the molecular weight is 117.7.

(Note 1) Tackifier: C9 petroleum resin, Alcon P140 (Arakawa Chemical Industries, Ltd., softening point 140 ° C., weight average molecular weight Mw: 900).
(Note 2) Polyisobutylene: “Tetrax 3T” (manufactured by Nippon Oil Corporation) (viscosity average molecular weight 30,000, weight average molecular weight, 49,000).

<Inner liner manufacturing method>
A thermoplastic elastomer composition such as SIBS-modified copolymer, SIBS, SIS, and SIB is converted into a twin-screw extruder (screw diameter: φ50 mm, L / D: 30, Cylinder temperature: 220 ° C.). Then, T-die extruder (screw diameter: φ80mm, L / D: 50, die lip width: 500mm, cylinder temperature: 220 ° C, film gauge: 0.25mm for the first layer, 2a layer and 2b layer, Also produced an inner liner at 0.05 mm).

  In order to adjust the thickness of the bead portion 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 manufactured. Was placed on the inner surface of the tire as an inner liner.

<Manufacture of pneumatic tires>
As the pneumatic tire, a 195 / 65R15 size tire having the basic structure shown in FIG. 1 was manufactured. A raw tire was produced using the polymer laminate as an inner liner, and press vulcanized at 170 ° C. for 20 minutes. Without removing the vulcanized tire from the vulcanization mold, it was cooled at 110 ° C. for 3 minutes and then removed from the vulcanization mold. Water was used as the cooling medium.

  Table 1 shows the contents of Comparative Formulations 1 to 6 and Implementation Formulations 1 to 8 in the first layer, and Table 2 shows the contents of Comparative Formulations 7 to 13 and Implementation Formulations 9 to 17 in the second layer. The tires of Examples and Comparative Examples were manufactured using these formulations in the first layer and the second layer. The specifications and results of performance evaluation are shown in Tables 3 to 4.

<Comparative Examples 1-5, Examples 1-9>
In Table 3, Comparative Examples 1 and 2 are examples of inner liners in which SIBS is used for the first layer, SIS is used for the second layer, and Gs / G is 1 and 0.5, respectively. Comparative Example 3 is an example of an inner liner using SIBS for the first layer and SIS for the second layer. Comparative Example 4 is an example of an inner liner using SIBS for the first layer and SIB for the second layer. Comparative Example 5 is an example of an inner liner using a SIBS-modified copolymer for the first layer and SIS for the second layer.

  Examples 1 to 4 are examples of inner liners using blends (practice blends 1 to 4) in which the SIS is used for the second layer and the elastomer component is changed for the first layer. Examples 5 to 9 are examples of an inner liner using a composition (implementation composition 6 to 10) in which SIBS is changed in the first layer and an elastomer component is changed in the second layer. It is recognized that Examples 1 to 9 of the present invention are generally excellent in weather resistance, flex crack growth resistance, air permeation resistance and rolling resistance.

<Comparative example 6, Examples 10-13>
In Table 4, Comparative Example 6 is an example of an inner liner in which Gs / G is 1 using the same formulation as Example 4 for the first layer and the second layer. Examples 10 to 13 are examples of inner liners in which the value of Gs / G was changed to the first layer and the second layer with the same composition as Comparative Example 6. It is recognized that Examples 10 to 13 are superior to Comparative Example 6 in terms of weather resistance, flex crack growth resistance, air permeation resistance and rolling resistance.

  In Tables 3 and 4, the values of the layer thickness of the first layer and the layer thickness of the second layer mean the average thickness from the tire crown portion to the bead portion excluding the buttress region (Rs).

<Performance test>
The following performance test was performed on the pneumatic tire manufactured as described above.

<Weather resistance test>
The inside of the tire inner liner was subjected to a weather resistance test under the following conditions using a Sunshine Super Long Life Weather Meter manufactured by Suga Test Instruments Co., Ltd. Irradiation was conducted for 60 minutes under conditions of rain for 12 minutes in a bath temperature of 63 ° C., humidity of 50%, and 60 ° C., and the number of cracks in the inner liner after the test was determined. Based on Comparative Example 1, the relative value of the number of cracks with other Comparative Examples and Examples was determined, and the weather resistance index was calculated based on the following formula. The larger the value, the better the weather resistance.

Weather resistance index = (number of cracks in comparative example 1) / (number of cracks in each example) × 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 properties of each Comparative Example and Example were 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 example) × 100
<Static air pressure drop rate test>
The 195 / 65R15 steel radial PC tire manufactured by the above method was assembled into a JIS standard rim 15 × 6 JJ, sealed with an initial air pressure of 300 Kpa, left at room temperature for 90 days, and the rate of decrease in air pressure was calculated.

<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 layer 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.

<Rolling resistance index>
Using a rolling resistance tester manufactured by Kobe Steel Co., Ltd., the prototype tire was assembled into a JIS standard rim 15 × 6JJ, and the load was 3.4 kN, the air pressure was 230 kPa, and the speed was 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 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
<Comprehensive judgment>
Judgment A means that all of the following conditions are satisfied.
(A) The weather resistance index is 105 or more.
(B) The flex crack growth index is 120 or more.
(C) Static air pressure reduction rate is less than 2.7.
(D) The rolling resistance index is 105 or more.

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.
(A) Weather resistance index is less than 100.
(B) The flex crack growth index is less than 120.
(C) Static air pressure reduction rate is 2.7 or more.
(D) The rolling resistance index is smaller than 105.

  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 2nd layer.

Claims (5)

In a pneumatic tire in which a carcass layer extending from the tread portion to the right and left bead portions, a belt layer outside the crown portion, and an inner liner inside the carcass layer,
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,
(A) The first layer is a SIBS in which a styrene block portion of a styrene-isobutylene-styrene block copolymer and a styrene-isobutylene-styrene block copolymer is modified with an acid chloride or acid anhydride having an unsaturated bond. An elastomer composition comprising a thermoplastic elastomer containing at least one of a modified copolymer, an ultraviolet absorber and an antioxidant,
(B) The second layer includes an elastomer containing at least one of a styrene-isoprene-styrene block copolymer and a styrene-isobutylene block copolymer,
The first layer and the second layer are an elastomer composition containing an ultraviolet absorber and an antioxidant in a total amount of 0.5% to 40% by weight of the elastomer component,
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 0.5 to 0.7. 3.   The pneumatic tire according to claim 1 or 2, wherein an average thickness Gs of a buttress region of the inner liner is 0.06 to 0.30 mm.   The air according to any one of claims 1 to 3, wherein the elastomer composition of any one of the first layer and the second layer contains a SIBS-modified copolymer in an amount of 5 mass% to 100 mass% of the elastomer component. Enter tire.   The pneumatic tire according to any one of claims 1 to 4, wherein the elastomer composition of any one of the first layer and the second layer is blended with a tackifier or polyisobutylene.

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