JP2009208734A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire made capable of restraining the augmentation in its mass while improving its durability. <P>SOLUTION: With respect to the pneumatic tire in which a carcass layer 4 is mounted between a pair of bead sections 3, 3 while a belt layer 7 is allocated around the outer circumference side of the carcass layer 4, an air permeation preventive layer 11 is allocated on the inner side face of the tire along the carcass layer 4, while an air permeation preventive layer 12 different from the air permeation preventive layer 11 is located at a position farther in the inner face side of the tire than the innermost side belt layer 7a in the direction of the diameter of the tire across a region B which includes at least the belt end region A, when the belt end regions A respectively having 3 mm of width are defined from the edge E of the belt layer 7a to outside and inside thereof in the direction of the width of the tire, the belt layer 7a, out of the belt layers 7, positioned at the innermost side in the direction of the diameter of the tire. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a carcass layer is mounted between a pair of bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer. More specifically, durability is improved while suppressing an increase in mass. The present invention relates to a pneumatic tire.

  A pneumatic tire has a casing structure in which a carcass layer is mounted between a pair of bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer. Usually, in order to prevent air leakage, a halogen is formed on the tire inner surface. An air permeation preventive layer (inner liner layer) made of low gas permeable rubber such as butyl rubber is provided. Further, in recent years, it has been proposed that a thin film made of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer with a thermoplastic resin is disposed on the tire inner surface as an air permeation prevention layer (inner liner layer) (for example, (See Patent Document 1 and Patent Document 2).

However, since the inner liner layer described above cannot completely prevent air permeation, air permeation occurs over time after the air is filled into the tire, and the coating rubber of the reinforcing layer such as the belt layer or the carcass layer is not contained in the tire. There is a tendency to deteriorate due to oxygen contained in the air that has permeated through. In particular, when the coated rubber at the end of the belt layer is deteriorated by oxygen, a separation failure is likely to occur at that portion, and the durability of the tire is significantly reduced. On the other hand, if the inner liner layer is made sufficiently thick, it is possible to suppress the above-described oxygen deterioration, but in this case, there is a drawback that the mass of the tire increases.
JP-A-8-217923 JP-A-11-199713

  An object of the present invention is to provide a pneumatic tire that can improve durability while suppressing an increase in mass.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire in which a carcass layer is mounted between a pair of bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer. A first air permeation prevention layer disposed on the inner surface of the tire, and a belt end having a width of 3 mm from the edge of the belt layer located on the innermost side in the tire radial direction to the outer side and the inner side in the tire width direction. When the region is defined, the second air permeation preventive layer different from the first air permeation preventive layer is at least on the tire inner surface side than the innermost belt layer in the tire radial direction over the region including the belt end region. It is characterized by having been arranged in.

  In the present invention, the first air permeation preventive layer is disposed along the carcass layer on the tire inner surface, while the second air permeation preventive layer different from the first air permeation preventive layer is at least in the tire radial direction over the region including the belt end region. By disposing on the inner surface of the tire with respect to the innermost belt layer, it is possible to prevent oxygen deterioration due to air permeation in the coat rubber at the end of the belt layer, thereby improving the durability of the pneumatic tire. it can. Moreover, since the 2nd air permeation prevention layer should just be selectively arrange | positioned only to the site | part which should prevent oxygen deterioration, the mass increase of a pneumatic tire can be suppressed.

  In the present invention, the second air permeation prevention layer is preferably composed of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending a thermoplastic resin and an elastomer. When these thermoplastic resins or thermoplastic elastomer compositions are used, the second air permeation prevention layer can be made thinner than when butyl rubber is used, so that the increase in tire mass can be minimized. Moreover, the shape of the belt layer can be kept flat as before.

  When the second air permeation prevention layer is composed of a thermoplastic elastomer composition, the volume ratio of the elastomer in the thermoplastic elastomer composition is preferably 55% to 95%. Thereby, the outstanding air permeation prevention performance can be exhibited, ensuring a favorable elastic modulus as a tire member.

  The second air permeation prevention layer is preferably disposed between the innermost belt layer in the tire radial direction and the carcass layer. Thereby, oxygen deterioration of a belt layer can be prevented effectively. The second air permeation preventive layer has a structure in which strip pieces are continuously wound in the tire circumferential direction, the strip pieces are arranged densely on the belt edge side, and the strip pieces are arranged loosely on the belt center side. Is preferred. In other words, the second air permeation preventive layer is preferably disposed over the entire width of the belt layer. However, when such a second air permeation preventive layer is added, it is difficult to inflate the tire during vulcanization. Therefore, in the strip winding method, the belt strip side is arranged densely and the strip central portion is sparsely arranged at the belt center side, thereby relaxing the tightening force by the second air permeation preventive layer. Oxygen deterioration of the layer can be effectively prevented.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIG. 2 shows an enlarged main part thereof. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 including a plurality of reinforcing cords is mounted between the pair of left and right bead portions 3 and 3, and the carcass layer 4 is wound around the bead core 5 from the inside to the outside of the tire. As the reinforcing cord for the carcass layer 4, an organic fiber cord such as a nylon cord or a polyester cord is generally used, but a steel cord may be used for a truck / bus tire. A bead filler 6 made of a rubber composition is disposed on the outer periphery of the bead core 5. On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 are arranged such that the reinforcing cords are inclined with respect to the tire circumferential direction, and the reinforcing cords cross each other between the layers. As the reinforcing cord for the belt layer 7, a steel cord is generally used, but an organic fiber cord such as an aramid cord may be used. Of these belt layers 7, the belt layer 7a located on the innermost side in the tire radial direction has a wider belt width than the belt layer 7b located on the outermost side in the tire radial direction.

  In the pneumatic tire, an air permeation preventive layer 11 (first air permeation preventive layer) is disposed along the carcass layer 4 on the inner surface of the tire. As a constituent material of the air permeation preventive layer 11, a thermoplastic resin or a thermoplastic elastomer composition can be used in addition to a rubber composition mainly composed of a low gas permeable rubber such as butyl rubber or halogenated butyl rubber.

  Here, when the belt end region A having a width of 3 mm is defined on the outer side and the inner side in the tire width direction from the edge E of the belt layer 7a located on the innermost side in the tire radial direction in the belt layer 7, the innermost tire radial direction is defined. An air permeation preventive layer 12 (second air permeation preventive layer) different from the air permeation preventive layer 11 is selectively provided over the region B including at least the belt end region A on the tire inner surface side of the inner belt layer 7a. Is arranged. The air permeation preventive layer 12 may be disposed over the entire width of the belt layer 7a. However, even if the air permeation preventive layer 12 is extended toward the region away from the belt layer 7, the protective effect on the belt layer 7 is not obtained, and only an increase in mass is caused. The protruding width C of the air permeation preventive layer 12 to the outer side in the tire width direction is preferably 15 mm or less.

  As described above, the air permeation preventive layer 11 is disposed on the tire inner surface along the carcass layer 4, while the air permeation preventive layer 12 different from this is disposed at least in the tire radial direction over the region B including the belt end region A. By disposing on the inner surface side of the tire with respect to the inner belt layer 7a, oxygen deterioration due to air permeation is prevented from occurring in the coat rubber at the end of the belt layer 7a, and thus the durability of the pneumatic tire is improved. be able to. In addition, since the air permeation preventive layer 12 may be selectively disposed only at the site where oxygen deterioration should be prevented, an increase in the mass of the pneumatic tire can be suppressed.

  As a constituent material of the air permeation preventive layer 12, it is possible to use a rubber composition mainly composed of a low gas permeable rubber such as halogenated butyl rubber. Particularly, a thermoplastic resin or a thermoplastic elastomer composition is used. It is preferable to do. When these thermoplastic resins or thermoplastic elastomer compositions are used, the air permeation preventive layer 12 can be made thinner than when butyl rubber is used. Therefore, even if the air permeation preventive layer 12 is added near the end of the belt layer 7, the increase in the mass of the tire can be minimized, and the shape of the belt layer 7 can be kept flat as before. .

  When the air permeation preventive layer 12 is composed of a thermoplastic elastomer composition, the volume ratio of the elastomer in the thermoplastic elastomer composition is preferably 55% to 95%. Thereby, the outstanding air permeation prevention performance can be exhibited, ensuring a favorable elastic modulus as a tire member. Here, if the volume ratio of the elastomer in the thermoplastic elastomer composition is less than 55%, the elastic modulus of the thin film is too high and it becomes difficult to use it as a tire member. descend.

  In the embodiment described above, the air permeation preventive layer 12 is disposed on the outer peripheral side of the carcass layer 4 so as to be in close contact with the carcass layer 4, but the air permeation preventive layer 12 is disposed on the innermost belt layer 7a in the tire radial direction. You may arrange | position so that it may closely_contact | adhere with this belt layer 7a on the inner peripheral side. As described above, when the air permeation preventive layer 12 is disposed between the innermost belt layer 7 a in the tire radial direction and the carcass layer 4, oxygen deterioration of the belt layer 7 can be effectively prevented. However, the air permeation preventive layer 12 may be disposed on the inner peripheral side of the carcass layer 4 so as to be in close contact with the carcass layer.

  The air permeation preventive layer 12 may be formed of a sheet material having a width substantially equal to that of the air permeation preventive layer 12, but a strip piece having a narrower width than the air permeation preventive layer 12 is formed in the tire circumferential direction. It is good also as a structure wound continuously around. In this case, it is preferable that the strip pieces are arranged densely on the belt edge side and the strip pieces are arranged sparsely on the belt center side.

  FIG. 3 schematically shows an air permeation preventive layer made of a strip material. 3, the air permeation preventive layer 12 has a structure in which a strip piece S having a narrower width than the air permeation preventive layer 12 is continuously wound in the tire circumferential direction, and the arrangement of the strip pieces S on the belt edge side. Is relatively dense, and the strip pieces S are relatively sparsely arranged on the belt center side. In this way, by arranging the strip pieces S densely on the belt edge side and sparsely arranging the strip pieces S on the belt center side, oxygen deterioration of the belt layer 7 while relaxing the tightening force by the air permeation preventive layer 12. Can be effectively prevented.

  Hereinafter, the thermoplastic resin or thermoplastic elastomer composition used for the air permeation preventive layer in the present invention will be described. The air permeation preventive layer can be composed of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending a thermoplastic resin and an elastomer.

  Examples of the thermoplastic resin used in the present invention include polyamide resins [for example, nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11), nylon 12 (N12), Nylon 610 (N610), Nylon 612 (N612), Nylon 6/66 copolymer (N6 / 66), Nylon 6/66/610 copolymer (N6 / 66/610), Nylon MXD6 (MXD6), Nylon 6T Nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer] and their N-alkoxyalkylated products, for example, methoxymethylated products of nylon 6, nylon 6/610 copolymers Methoxymethylated product of nylon 612, methoxymethylated product of nylon 612, polyester resin [for example, poly Tylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET / PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, polyoxyalkylene diimide diacid / Aromatic polyesters such as polybutylene terephthalate copolymer], polynitrile resins [for example, polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), (meth) acrylonitrile / styrene copolymer, (Meth) acrylonitrile / styrene / butadiene copolymer], polymethacrylate resin [for example, polymethyl methacrylate (PMMA), polyethyl methacrylate], polyvinyl resin [for example, acetic acid Nyl, polyvinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PDVC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate copolymer , Vinylidene chloride / acrylonitrile copolymer (ETFE)], cellulose resin [eg, cellulose acetate, cellulose acetate butyrate], fluorine resin [eg, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoro Ethylene (PCTFE), tetrafluoroethylene / ethylene copolymer], an imide resin [for example, aromatic polyimide (PI)] and the like can be preferably used.

  Examples of the elastomer used in the present invention include diene rubber and hydrogenated products thereof [for example, natural rubber (NR), isoprene rubber (IR), epoxidized natural rubber, styrene butadiene rubber (SBR), butadiene rubber ( BR, high cis BR and low cis BR), nitrile rubber (NBR), hydrogenated NBR, hydrogenated SBR], olefin rubber [for example, ethylene propylene rubber (EPDM, EPM), maleic acid modified ethylene-α olefin copolymerization Rubber, maleic acid-modified ethylene propylene rubber (M-EPM), butyl rubber (IIR), isobutylene and aromatic vinyl or diene monomer copolymer, acrylic rubber (ACM), ionomer], halogen-containing rubber [for example, Br-IIR Of CI-IIR, isopropylene paramethylstyrene copolymer Dioxide, brominated isobutylene paramethylstyrene copolymer (Br-IPMS), chloroprene rubber (CR), hydrin rubber (CHR), chlorosulfonated polyethylene rubber (CSM), chlorinated polyethylene rubber (CM), maleic acid modified Chlorinated polyethylene rubber (M-CM)], silicon rubber [for example, methyl vinyl silicon rubber, dimethyl silicon rubber, methyl phenyl vinyl silicon rubber], sulfur-containing rubber [for example, polysulfide rubber], fluorine rubber [for example, vinylidene fluoride type Rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorine-containing silicon rubber, fluorine-containing phosphazene rubber), thermoplastic elastomer (for example, styrene elastomer, olefin elastomer, esthetic And the like can be preferably used.

  When the above-mentioned specific thermoplastic resin and elastomer are different in compatibility, they can be made compatible by using an appropriate compatibilizing agent as the third component. By mixing the compatibilizer with the blend system, the interfacial tension between the thermoplastic resin and the elastomer decreases, and as a result, the rubber particle size forming the dispersion layer becomes finer, so the characteristics of both components are more It will be expressed effectively. Such a compatibilizing agent generally includes a copolymer having a structure of both or one of a thermoplastic resin and an elastomer, or an epoxy group, a carbonyl group, a halogen group, and an amino group that can react with the thermoplastic resin or elastomer. In addition, a copolymer having an oxazoline group, a hydroxyl group and the like can be taken. These may be selected according to the type of thermoplastic resin and elastomer to be mixed, but those commonly used include styrene / ethylene butylene block copolymer (SEBS) and its maleic acid modified product, EPDM, EPM, EPDM / styrene or EPDM / acrylonitrile graft copolymer and its modified maleic acid, styrene / maleic acid copolymer, reactive phenoxin and the like can be mentioned. The amount of the compatibilizing agent is not particularly limited, but preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the polymer component (the total of the thermoplastic resin and the elastomer).

  In the thermoplastic elastomer composition, the composition ratio between the specific thermoplastic resin and the elastomer is not particularly limited, and is appropriately determined so as to have a structure in which the elastomer is dispersed as a discontinuous phase in the thermoplastic resin matrix. The preferred range is 90/10 to 30/70 by weight.

  In the present invention, the thermoplastic resin and the thermoplastic elastomer composition constituting the air permeation preventive layer can be mixed with other polymers such as the above-mentioned compatibilizing agent as long as the necessary properties as a tire member are not impaired. . The purpose of mixing other polymers is to improve the compatibility between the thermoplastic resin and the elastomer, to improve the molding processability of the material, to improve the heat resistance, to reduce the cost, etc. Examples of the material that can be used include polyethylene (PE), polypropylene (PP), polystyrene (PS), ABS, SBS, and polycarbonate (PC). In addition, fillers (calcium carbonate, titanium oxide, alumina, etc.) generally incorporated into polymer blends, reinforcing agents such as carbon black and white carbon, softeners, plasticizers, processing aids, pigments, dyes, and aging An inhibitor or the like can be arbitrarily blended as long as necessary characteristics as a tire member are not impaired.

  The elastomer can also be dynamically vulcanized when mixed with the thermoplastic resin. The vulcanizing agent, vulcanization aid, vulcanization conditions (temperature, time), and the like in the case of dynamic vulcanization may be appropriately determined according to the composition of the elastomer to be added, and are not particularly limited.

  A general rubber vulcanizing agent (crosslinking agent) can be used as the vulcanizing agent. Specific examples of the sulfur vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, alkylphenol disulfide, and the like. 4 phr [In the present specification, “phr” refers to parts by weight per 100 parts by weight of the elastomer component. same as below. ] Can be used.

  Organic peroxide vulcanizing agents include benzoyl peroxide, t-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-di (t-butyl peroxide). Oxy) hexane, 2,5-dimethylhexane-2,5-di (peroxylbenzoate) and the like are exemplified, and for example, about 1 to 20 phr can be used.

  Furthermore, examples of the phenol resin-based vulcanizing agent include bromides of alkyl phenol resins, mixed crosslinking systems containing halogen donors such as tin chloride and chloroprene, and alkyl phenol resins. For example, about 1 to 20 phr is used. Can do.

  In addition, zinc white (about 5 phr), magnesium oxide (about 4 phr), risurge (about 10 to 20 phr), p-quinonedioxime, p-dibenzoylquinonedioxime, tetrachloro-p-benzoquinone, poly-p- Examples include dinitrosobenzene (about 2 to 10 phr) and methylene dianiline (about 0.2 to 10 phr).

  Moreover, you may add a vulcanization accelerator as needed. Examples of the vulcanization accelerator include general vulcanization accelerators such as aldehyde / ammonia, guanidine, thiazole, sulfenamide, thiuram, dithioate, thiourea, etc. About 2 phr can be used.

  Specifically, as the aldehyde / ammonia vulcanization accelerator, hexamethylenetetramine and the like, as the guanidinium vulcanization accelerator, diphenyl guanidine, etc., as the thiazole vulcanization accelerator, dibenzothiazyl disulfide ( DM), 2-mercaptobenzothiazole and its Zn salt, cyclohexylamine salt and the like, sulfenamide vulcanization accelerators include cyclohexylbenzothiazylsulfenamide (CBS), N-oxydiethylenebenzothiazyl-2- As thiuram vulcanization accelerators such as sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, 2- (thymolpolynyldithio) benzothiazole, tetramethylthiuram disulfide (TMTD), tetraethyl Thiuram disulfide, tetrame Examples of dithioate-based vulcanization accelerators such as lutiuram monosulfide (TMTM) and dipentamethylene thiuram tetrasulfide include Zn-dimethyldithiocarbamate, Zn-diethyldithiocarbamate, Zn-di-n-butyldithiocarbamate, Zn -Ethyl phenyl dithiocarbamate, Te-diethyl dithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate, pipecoline pipecolyldithiocarbamate, etc. Examples of thiourea vulcanization accelerators include ethylenethiourea and diethylthiourea be able to.

  Moreover, as a vulcanization | cure acceleration | stimulation adjuvant, the general rubber adjuvant can be used together, for example, zinc white (about 5 phr), stearic acid, oleic acid, and these Zn salts (about 2-4 phr). Etc. can be used.

A method for producing a thermoplastic elastomer composition includes a thermoplastic resin in which a thermoplastic resin and an elastomer (unvulcanized in the case of rubber) are melt-kneaded in advance using a twin-screw kneading extruder or the like to form a continuous phase (matrix). By dispersing the elastomer as a dispersed phase (domain) in it. When the elastomer is vulcanized, a vulcanizing agent may be added under kneading to dynamically vulcanize the elastomer. Further, various compounding agents (excluding the vulcanizing agent) for the thermoplastic resin or elastomer may be added during the kneading, but it is preferable to mix them in advance before kneading. The kneading machine used for kneading the thermoplastic resin and the elastomer is not particularly limited, and a screw extruder, a kneader, a Banbury mixer, a biaxial kneading extruder, or the like can be used. Among them, it is preferable to use a twin-screw kneading extruder for kneading the thermoplastic resin and the elastomer and for dynamic vulcanization of the elastomer. Further, two or more types of kneaders may be used and kneaded sequentially. As conditions for melt kneading, the temperature may be higher than the temperature at which the thermoplastic resin melts. The shear rate during kneading is preferably 1000 to 7500 sec ⁻¹ . The entire kneading time is from 30 seconds to 10 minutes, and when a vulcanizing agent is added, the vulcanization time after addition is preferably from 15 seconds to 5 minutes. The polymer composition produced by the above method may be formed into a desired shape by a general thermoplastic resin molding method such as injection molding or extrusion molding.

  The thermoplastic elastomer composition thus obtained has a structure in which an elastomer is dispersed as a discontinuous phase in a matrix of a thermoplastic resin. By taking such a structure, it is possible to provide sufficient rigidity as a tire member and sufficient rigidity due to the effect of the resin layer as a continuous phase, and at the time of molding, regardless of the amount of elastomer, Equivalent moldability can be obtained.

  The Young's modulus of the thermoplastic resin and the thermoplastic elastomer composition is not particularly limited, but is preferably 1 to 500 MPa, more preferably 50 to 500 MPa.

  The thermoplastic resin or thermoplastic elastomer composition can be formed into a sheet or film and used alone, but an adhesive layer may be laminated to improve the adhesion to the adjacent rubber. Specific examples of the adhesive polymer constituting the adhesive layer include ultrahigh molecular weight polyethylene (UHMWPE), ethylene ethyl acrylate copolymer (EEA), ethylene methyl acrylate resin (EMA) having a molecular weight of 1 million or more, preferably 3 million or more. ), Acrylate copolymers such as ethylene acrylic acid copolymer (EAA) and their maleic anhydride adducts, polypropylene (PP) and its maleic acid modification, ethylene propylene copolymer and its maleic acid modification, Polybutadiene resin and its modified maleic anhydride, styrene-butadiene-styrene copolymer (SBS), styrene-ethylene-butadiene-styrene copolymer (SEBS), fluorine thermoplastic resin, polyester thermoplastic resin, etc. Can be mentioned. These can be extruded into a sheet form or a film form by a conventional method, for example, using a resin extruder. The thickness of the adhesive layer is not particularly limited, but it is preferable that the thickness is small for weight reduction of the tire, and 5 μm to 150 μm is preferable.

  In a pneumatic tire having a tire size of 195 / 65R15, in which a carcass layer is mounted between a pair of bead portions, and two belt layers are disposed on the outer peripheral side of the carcass layer, on the tire inner surface along the carcass layer The tires of the conventional examples, Examples 1 to 5 and Comparative Examples 1 and 2 in which the configurations of the first air permeation preventive layer positioned and the second air permeation preventive layer positioned in the belt end region are varied. Produced.

  In the conventional tire, a first air permeation preventive layer made of butyl rubber and having a thickness of 0.5 mm is disposed on the inner surface of the tire along the carcass layer, but a second air permeation preventive layer is not provided. .

  In the tire of Example 1, a first air permeation prevention layer made of butyl rubber and having a thickness of 0.5 mm is disposed on the inner surface of the tire along the carcass layer, while second air made of butyl rubber and having a thickness of 0.5 mm. The permeation preventive layer is disposed between the belt layer and the carcass layer in a region having a width of 3 mm (± 3 mm) on the outer side and the inner side in the tire width direction from the edge of the innermost belt layer in the tire radial direction. .

  In the tire of Example 2, the first air permeation prevention layer made of butyl rubber having a thickness of 0.5 mm is disposed on the inner surface of the tire along the carcass layer, while the thermoplastic resin (nylon 6, 66) and the elastomer (bromine). A second air permeation preventive layer made of a thermoplastic elastomer composition blended with a butyl rubber) between the belt layer and the carcass layer and from the edge of the innermost belt layer in the tire radial direction. It is arranged in a region having a width of 3 mm (± 3 mm) on the outer side and the inner side in the tire width direction.

  In the tire of Example 3, the first air permeation prevention layer made of butyl rubber having a thickness of 0.5 mm is disposed on the tire inner surface along the carcass layer, while the thermoplastic resin (vinyl alcohol / ethylene copolymer) is used. The second air permeation preventive layer having a thickness of 0.005 mm is provided between the belt layer and the carcass layer, with a width of 3 mm (± 3 mm).

  In the tire of Example 4, the first air permeation preventive layer having a thickness of 0.05 mm made of a thermoplastic elastomer composition obtained by blending a thermoplastic resin (nylon 6, 66) and an elastomer (brominated butyl rubber) is used as a carcass layer. The second air permeation prevention layer made of the same thermoplastic elastomer composition and having a thickness of 0.05 mm is disposed between the belt layer and the carcass layer and is located on the innermost side in the tire radial direction. It is arranged in a region having a width of 3 mm (± 3 mm) on the outer side and the inner side in the tire width direction from the edge of the belt layer.

  In the tire of Example 5, the first air permeation prevention layer made of a thermoplastic resin (vinyl alcohol / ethylene copolymer) having a thickness of 0.005 mm is disposed on the tire inner surface along the carcass layer. A second air permeation preventive layer made of a plastic resin and having a thickness of 0.005 mm is provided between the belt layer and the carcass layer and 3 mm from the edge of the innermost belt layer in the tire radial direction to the outer side and the inner side in the tire width direction. It is arranged in an area having a width (± 3 mm).

  In the tire of Comparative Example 1, the first air permeation preventive layer made of butyl rubber having a thickness of 0.8 mm is disposed on the tire inner surface along the carcass layer, but the second air permeation preventive layer is not provided. is there.

  In the tire of Comparative Example 2, a first air permeation prevention layer made of butyl rubber and having a thickness of 0.5 mm is disposed on the inner surface of the tire along the carcass layer, while second air made of butyl rubber and having a thickness of 0.5 mm. The permeation preventive layer is disposed between the belt layer and the carcass layer in a region having a width of 2 mm (± 2 mm) from the edge of the innermost belt layer in the tire radial direction to the outer side and the inner side in the tire width direction. .

  The tires of the above-described conventional examples, Examples 1 to 5 and Comparative Examples 1 and 2 were measured for mass, evaluated for durability by the following evaluation method, and the results are shown in Table 1.

durability:
Each test tire was assembled on a wheel with a rim size of 15 × 6J, oxygen was sealed in the tire at 350 kPa, and left at 80 ° C. for 5 days. The distance traveled until this occurred. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the durability.

  As is clear from Table 1, the tires of Examples 1 to 5 were superior in durability to the conventional examples, and the increase in mass was slight. On the other hand, the tire of Comparative Example 1 is superior in durability to the conventional example, but has a large increase in mass. The tire of Comparative Example 2 was not sufficient although an effect of improving durability was observed.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is sectional drawing which shows the principal part of the pneumatic tire of FIG. It is sectional drawing which shows schematically the air permeation prevention layer comprised from the strip material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 11 1st air permeation prevention layer 12 2nd air permeation prevention layer

Claims (5)

  In a pneumatic tire in which a carcass layer is mounted between a pair of bead portions and a belt layer is disposed on the outer peripheral side of the carcass layer, a first air permeation prevention layer is disposed on the tire inner surface along the carcass layer. When the belt end region having a width of 3 mm is defined on the outer side and the inner side in the tire width direction from the edge of the belt layer located on the innermost side in the tire radial direction of the belt layer, the first air permeation prevention layer and A pneumatic tire, wherein a different second air permeation prevention layer is disposed on the tire inner surface side of the innermost belt layer in the tire radial direction over a region including at least the belt end region.   2. The pneumatic tire according to claim 1, wherein the second air permeation prevention layer is made of a thermoplastic elastomer composition obtained by blending a thermoplastic resin or a thermoplastic resin and an elastomer.   The pneumatic tire according to claim 2, wherein the second air permeation prevention layer is made of a thermoplastic elastomer composition, and a volume ratio of the elastomer in the thermoplastic elastomer composition is 55% to 95%. .   The pneumatic tire according to claim 1, wherein the second air permeation preventive layer is disposed between the innermost belt layer in the tire radial direction and the carcass layer.   The second air permeation preventive layer has a structure in which strip pieces are continuously wound in the tire circumferential direction, the arrangement of the strip pieces is dense on the belt edge side, and the arrangement of the strip pieces is sparse on the belt center side. The pneumatic tire according to any one of claims 1 to 4, wherein:

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