JP7180151B2 - pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire provided with a film layer on the inner surface of the tire, which is made of a thermoplastic resin or a thermoplastic elastomer composition in which an elastomer is blended in a thermoplastic resin. and prevent peeling of the film layer during running.

In a pneumatic tire, it is common to arrange an air permeation prevention layer made of butyl rubber inside the carcass layer, but in recent years, a thermoplastic resin or a thermoplastic resin blended with an elastomer in the carcass layer has been used on the inside of the carcass layer. It has been proposed to dispose an air permeation prevention layer comprising a film of a plastic elastomer composition (see, for example, Patent Documents 1 to 3). Such an air permeation preventing layer made of a film of a thermoplastic resin material greatly contributes to weight reduction of the tire.

By the way, since pneumatic tires for motor sports do not require long-term air retention ability, the air permeation prevention layer made of butyl rubber is eliminated for the purpose of weight reduction. There is a demerit that sometimes the bladder slides poorly against the inner surface of the tire, and the carcass line is not formed as designed. Therefore, in a pneumatic tire for motor sports, by arranging a film layer of a thermoplastic resin or a thermoplastic elastomer composition in which an elastomer is blended in a thermoplastic resin on the inner surface of the tire, while achieving weight reduction, the tire Attempts have been made to improve the slippage of the bladder against the inner surface of the tire during vulcanization. In addition, since the film layer contributes to an increase in tire rigidity, an effect of improving steering stability is expected.

However, especially in pneumatic tires for motor sports, the temperature of the tire itself becomes high during running. There is an inconvenience that the film layer is peeled off from the inner surface of the tire.

Japanese Patent Application Laid-Open No. 2007-30636 JP 2007-50614 A JP 2007-99146 A

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire which is improved in steering stability by adding a film layer and which can prevent peeling of the film layer during running.

The pneumatic tire of the present invention for achieving the above object comprises a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and these sidewall portions. A pneumatic tire comprising a pair of bead portions arranged radially inward of the tire, wherein a film layer made of a thermoplastic resin or a thermoplastic elastomer composition in which an elastomer is blended in a thermoplastic resin is arranged on the inner surface of the tire A plurality of through-holes are formed along the tire circumferential direction in at least a partial region of the film layer in the tire radial direction, and the maximum dimension of each of the through-holes is 0.1 mm to 1.0 mm. and wherein the through-hole forms a space containing no rubber .

In the present invention, a film layer made of a thermoplastic resin or a thermoplastic elastomer composition is disposed on the inner surface of the tire. Steering stability can be improved by increasing tire stiffness. Moreover, since a plurality of through holes are formed along the tire circumferential direction in at least a portion of the film layer in the tire radial direction, air remaining between the film layer and the carcass layer penetrates during tire molding. It is discharged to the tire cavity side through the hole. Therefore, when the temperature of the tire itself becomes high during running, expansion of air pockets between the film layer and the carcass layer can be avoided, and peeling of the film layer during running can be effectively prevented. . In addition, the film layer does not function as an air permeation prevention layer, but is provided for the purpose of improving the slippage of the bladder during tire vulcanization and obtaining a reinforcing effect. through holes are formed, there is no problem.

In the present invention, the maximum dimension of each through-hole is preferably 0.1 mm to 1.0 mm. By setting the maximum dimension of each of the through-holes within the above range, it is possible to ensure sufficient tire rigidity while effectively preventing the film layer from peeling off.

Further, it is preferable that the number of through-holes arranged per 100 cm ² is 1 to 400 in at least a part of the area where the through-holes are formed. By setting the number of through-holes arranged per 100 cm ² within the above range, it is possible to effectively prevent peeling of the film layer while ensuring sufficient tire rigidity.

1 is a meridian sectional view showing a pneumatic tire for motor sports according to an embodiment of the present invention; FIG. FIG. 2 is a side view showing the inner surface of the pneumatic tire of FIG. 1; It is sectional drawing which expands and shows the A section of FIG. FIG. 3 is a plan view showing an enlarged portion B of FIG. 2;

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire for motor sports according to an embodiment of the present invention, and FIGS. 2 to 4 show the essential parts thereof.

As shown in FIG. 1, the pneumatic tire of this embodiment includes a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1. and a pair of bead portions 3 , 3 arranged radially inward of the sidewall portions 2 .

A carcass layer 4 is mounted between the pair of bead portions 3,3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the tire inner side to the outer side around bead cores 5 arranged in the respective bead portions 3 . In the carcass layer 4, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set within a range of 75° to 90°, for example. As the reinforcing cords for the carcass layer 4, organic fiber cords made of rayon, polyester, aromatic polyamide or the like are preferably used. The carcass layer 4 has a main body portion 4a and a winding portion 4b bounded by the bead core 5. As shown in FIG.

In each bead portion 3, a bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer circumference of the bead core 5, and the bead filler 6 is sandwiched between the main portion 4a and the winding portion 4b of the carcass layer 4. there is An organic fiber reinforcing layer 7 including organic fiber cords inclined with respect to the tire circumferential direction is embedded in the bead portion 3 so as to wrap the bead core 5 and the bead filler 6 .

On the other hand, a plurality of belt layers 8 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1 . These belt layers 8 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords intersect each other between the layers. In the belt layer 8, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set within a range of, for example, 10° to 40°. A steel cord is preferably used as the reinforcing cord for the belt layer 8 . At least one belt cover layer 9 formed by arranging reinforcing cords at an angle of, for example, 5° or less with respect to the tire circumferential direction is arranged on the outer peripheral side of the belt layer 8 for the purpose of improving high-speed durability. there is Organic fiber cords such as nylon and aramid cords are preferably used as the reinforcing cords for the belt cover layer 9 .

The tire internal structure described above is a representative example of a pneumatic tire, but is not limited to this.

In the above pneumatic tire, inside the carcass layer 4, a reinforcing film layer 11 made of a thermoplastic resin or a thermoplastic elastomer composition in which an elastomer is blended in the thermoplastic resin, and the film layer 11 as a carcass layer. 4 and an inner liner layer 10 (see FIG. 3) which is laminated with a tie rubber layer 12 for adhesion.

As shown in FIGS. 2 to 4, a plurality of through holes 13 are formed along the tire circumferential direction in at least a part of the film layer 11 in the tire radial direction. The tire radial direction referred to here means the tire meridian direction. The through-holes 13 need to be formed in at least a partial region of the film layer 11 in the tire radial direction, but are preferably formed in at least the shoulder region S of the film layer 11 . It is more preferable to form the Since the shoulder region S is the region where the bladder comes into contact with the inner surface of the tire last during vulcanization, air tends to remain therein. Therefore, by arranging the through holes 13 at least in the shoulder region S of the film layer 11, the effect of preventing the film layer 11 from being peeled off can be effectively exhibited. In addition, the through-hole 13 is described as space in FIG .

In the pneumatic tire described above, since the reinforcing film layer 11 made of a thermoplastic resin or a thermoplastic elastomer composition is disposed on the inner surface of the tire, it is possible to prevent a significant increase in tire mass during tire vulcanization. In addition, the addition of the film layer 11 increases tire rigidity and improves steering stability.

Moreover, since a plurality of through-holes 13 are formed along the tire circumferential direction in at least a part of the film layer 11 in the tire radial direction, air remaining between the film layer 11 and the carcass layer 4 is eliminated. It is discharged to the tire cavity side through the through holes 13 during tire molding. Therefore, when the temperature of the tire itself becomes high during running, expansion of air pools between the film layer 11 and the carcass layer 4 is avoided, and peeling of the film layer 11 during running is effectively prevented. be able to. In particular, since a pneumatic tire for motor sports becomes hot during running, it is effective to prevent peeling of the film layer 11 due to the heat generation.

Further, in a pneumatic tire for motor sports, the film layer 11 does not function as an air permeation prevention layer, but is provided for the purpose of improving the slippage of the bladder during tire vulcanization and obtaining a reinforcing effect. Therefore, even if a large number of through holes 13 are formed in the film layer 11, there is no problem.

In the above pneumatic tire, the maximum dimension D of each through-hole 13 is preferably 0.1 mm to 1.0 mm. By setting the maximum dimension D of each of the through-holes 13 within the above range, it is possible to effectively prevent peeling of the film layer 11 while ensuring sufficient tire rigidity. If the maximum dimension D of the through-hole 13 is smaller than 0.1 mm, the air leakage becomes poor, and conversely, if it is larger than 1.0 mm, tire rigidity is lowered. The shape of the through hole 13 is not particularly limited, and may be circular, elliptical, oval, rectangular, polygonal, or the like, for example. If the through hole 13 is circular, the maximum dimension D is the diameter. When the through hole 13 is elliptical or oval, the maximum dimension D is the major axis. Further, the through-holes 13 can be formed in desired regions of the film layer 11 by, for example, pricking the film layer 11 at a material stage before the tire molding process.

Further, it is preferable that the number of through-holes 13 arranged per 100 cm ² in at least a partial area where the through-holes 13 are formed is 1 to 400. By setting the number of through-holes 13 arranged per 100 cm ² within the above range, it is possible to effectively prevent peeling of the film layer 11 while ensuring sufficient tire rigidity. If the number of through-holes 13 arranged per 100 cm ² is less than 1, air leakage becomes poor, and if it is more than 400, the tire rigidity decreases.

In the above-described embodiments, pneumatic tires for motor sports have been described, but the present invention can also be applied to pneumatic tires for uses other than motor sports. Pneumatic tires used for purposes other than motor sports are generally required to retain air for a long period of time, but the film layer 11 having the through-holes 13 does not sufficiently function as an air permeation prevention layer. Therefore, such a pneumatic tire needs to be provided with an air permeation prevention layer extending along the carcass layer 4 in addition to the reinforcing film layer 11 .

The film layer 11 used in the present invention will be described below. The film layer 11 can be composed of a thermoplastic resin or a thermoplastic elastomer composition in which a thermoplastic resin and an elastomer are blended.

Examples of thermoplastic resins used in the present invention include polyamide resins [e.g., 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 [e.g., methoxymethylated nylon 6, nylon 6/610 copolymer methoxymethylated product, nylon 612 methoxymethylated product], polyester resin [e.g., polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET/PEI copolymer, polyarylate (PAR ), polybutylene naphthalate (PBN), liquid crystal polyester, aromatic polyester such as polyoxyalkylene diimide diacid / polybutylene terephthalate copolymer], polynitrile resin [e.g., polyacrylonitrile (PAN), polymethacrylonitrile, Acrylonitrile/styrene copolymer (AS), (meth)acrylonitrile/styrene copolymer, (meth)acrylonitrile/styrene/butadiene copolymer], polymethacrylate resin [e.g., polymethyl methacrylate (PMMA), polymethacrylic ethyl acid], polyvinyl-based resin [e.g., polyvinyl acetate, polyvinyl alcohol (PVA), vinyl alcohol/ethylene copolymer (EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride/vinylidene chloride copolymers, vinylidene chloride/methyl acrylate copolymers, vinylidene chloride/acrylonitrile copolymers], cellulose resins [e.g. cellulose acetate, cellulose acetate butyrate], fluorine resins [e.g. polyvinylidene fluoride (PVDF), polyfluoride vinyl chloride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene/ethylene copolymer (ETFE)], imide-based resins [eg, aromatic polyimide (PI)], and the like can be preferably used.

Elastomers used in the present invention include, for example, diene rubbers and hydrogenated products thereof [e.g., 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], olefinic rubber [e.g., ethylene propylene rubber (EPDM, EPM), 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 [e.g., Br-IIR, Cl-IIR, isobutylene-p-methylstyrene copolymer Coalescing Bromide (Br-IPMS), Chloroprene Rubber (CR), Hydrin Rubber (CHR), Chlorosulfonated Polyethylene Rubber (CSM), Chlorinated Polyethylene Rubber (CM), Maleic Acid Modified Chlorinated Polyethylene Rubber (M-CM) ], silicone rubber [e.g., methyl vinyl silicone rubber, dimethyl silicone rubber, methylphenyl vinyl silicone rubber], sulfur-containing rubber [e.g., polysulfide rubber], fluorine rubber [e.g., vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetra fluoroethylene-propylene rubber, fluorine-containing silicon rubber, fluorine-containing phosphazene rubber], thermoplastic elastomers [e.g., styrene elastomers, olefin elastomers, ester elastomers, urethane elastomers, polyamide elastomers], etc. are preferably used. can do.

When the compatibility between the specific thermoplastic resin and the elastomer is different, a suitable compatibilizing agent can be used as the third component to make them compatible. By adding a compatibilizer to the blend system, the interfacial tension between the thermoplastic resin and the elastomer is lowered, and as a result, the rubber particles forming the dispersed phase become finer, so the properties of both components are enhanced. effectively expressed. Such compatibilizers generally include copolymers having a structure of either or both of a thermoplastic resin and an elastomer, or epoxy groups, carbonyl groups, halogen groups, amino groups capable of reacting with thermoplastic resins or elastomers. , an oxazoline group, a hydroxyl group, or the like. These may be selected depending on the type of thermoplastic resin and elastomer to be mixed, but commonly used ones include styrene/ethylene-butylene block copolymer (SEBS) and its maleic acid modified products, EPDM, EPM, Examples include EPDM/styrene or EPDM/acrylonitrile graft copolymers and maleic acid-modified products thereof, styrene/maleic acid copolymers, reactive phenoxine, and the like. The amount of the compatibilizing agent to be blended is not particularly limited, but is 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 of 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 matrix of the thermoplastic resin. but the preferred range is 90/10 to 15/85 by weight.

In the present invention, the thermoplastic resin and thermoplastic elastomer composition that constitute the film may be mixed with other polymers such as a compatibilizer. 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, and to reduce the cost. Examples of materials that can be used include polyethylene (PE), polypropylene (PP), polystyrene (PS), ABS, SBS, polycarbonate (PC), and the like. In addition, fillers (calcium carbonate, titanium oxide, alumina, etc.), reinforcing agents such as carbon black and white carbon, softeners, plasticizers, processing aids, pigments, dyes, aging agents, etc., which are generally blended in polymer formulations An inhibitor or the like may optionally be added.

Elastomers can also be dynamically vulcanized when mixed with thermoplastic resins. Vulcanizing agents, vulcanizing auxiliaries, vulcanizing conditions (temperature, time) and the like for dynamic vulcanization may be appropriately determined according to the composition of the elastomer to be added, and are not particularly limited.

As the vulcanizing agent, a general rubber vulcanizing agent (crosslinking agent) can be used. Specifically, examples of sulfur-based vulcanizing agents 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.

Examples of organic peroxide-based 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 brominated alkylphenol resins, mixed cross-linking systems containing halogen donors such as tin chloride and chloroprene, and alkylphenol resins. can be done.

Others include zinc oxide (about 5 phr), magnesium oxide (about 4 phr), litharge (about 10-20 phr), p-quinonedioxime, p-dibenzoylquinonedioxime, tetrachloro-p-benzoquinone, poly-p- Examples include dinitrosobenzene (about 2 to 10 phr) and methylenedianiline (about 0.2 to 10 phr).

Moreover, you may add a vulcanization accelerator as needed. As vulcanization accelerators, general vulcanization accelerators such as aldehyde/ammonia-based, guanidine-based, thiazole-based, sulfenamide-based, thiuram-based, dithioate-based, and thiourea-based agents are used. About 2 phr can be used.

Specifically, aldehyde/ammonia-based vulcanization accelerators include hexamethylenetetramine and the like, guanidine-based vulcanization accelerators include diphenylguanidine and the like, and thiazole-based vulcanization accelerators include dibenzothiazyldisulfide ( DM), 2-mercaptobenzothiazole and its Zn salt, cyclohexylamine salt, and sulfenamide vulcanization accelerators such as cyclohexylbenzothiazylsulfenamide (CBS), N-oxydiethylenebenzothiazyl-2- Thiuram vulcanization accelerators such as sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, 2-(thymolpolynyldithio)benzothiazole, tetramethylthiuram disulfide (TMTD), tetraethyl Thiuram disulfide, tetramethylthiuram monosulfide (TMTM), dipentamethylene thiuram tetrasulfide, etc., and dithioate vulcanization accelerators such as Zn-dimethyldithiocarbamate, Zn-diethyldithiocarbamate, Zn-di-n- butyl dithiocarbamate, Zn-ethylphenyl dithiocarbamate, Te-diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate, pipecoline pipecolyl dithiocarbamate; Diethylthiourea and the like can be mentioned.

In addition, general rubber auxiliaries can be used together as vulcanization accelerator auxiliaries. etc. can be used.

A thermoplastic elastomer composition is produced by melt-kneading a thermoplastic resin and an elastomer (unvulcanized in the case of rubber) with a twin-screw kneading extruder or the like to form a continuous phase (matrix). By dispersing the elastomer as dispersed phases (domains) therein. When vulcanizing an elastomer, a vulcanizing agent may be added under kneading to dynamically vulcanize the elastomer. Various compounding agents (except vulcanizing agents) for the thermoplastic resin or elastomer may be added during kneading, but are preferably mixed in advance before kneading. A kneader used for kneading the thermoplastic resin and the elastomer is not particularly limited, and a screw extruder, a kneader, a Banbury mixer, a twin-screw kneading extruder and 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 dynamic vulcanization of the elastomer. Further, two or more types of kneaders may be used for kneading sequentially. As a condition for melt-kneading, the temperature should be equal to or higher than the temperature at which the thermoplastic resin melts. Also, the shear rate during kneading is preferably 1000 to 7500 sec ^-1 . The total kneading time is preferably 30 seconds to 10 minutes, and when a vulcanizing agent is added, the vulcanization time after addition is preferably 15 seconds to 5 minutes. The polymer composition produced by the above method may be formed into a desired shape by a conventional thermoplastic resin molding method such as injection molding or extrusion molding.

The thermoplastic elastomer composition thus obtained has a structure in which the elastomer is dispersed as a discontinuous phase in a thermoplastic resin matrix. By adopting such a structure, it is possible to provide both sufficient flexibility as a tire constituent 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, thermoplastic resin It is possible to obtain the same moldability as

The Young's modulus of the thermoplastic resin and thermoplastic elastomer composition in a standard atmosphere as defined by JIS K7100 is not particularly limited, but is preferably 1 to 500 MPa, more preferably 50 to 500 MPa.

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

A tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged inside the tire radial direction of the sidewall portions. A pneumatic tire for motor sports provided with a reinforcing film layer made of a thermoplastic elastomer composition in which an elastomer is blended in a thermoplastic resin is disposed on the inner surface of the tire, and a plurality of through holes are provided throughout the film layer were formed, and tires of Examples 1 to 13 were manufactured in which the maximum dimension D of the through holes and the number of through holes arranged per 100 cm ² were varied as shown in Tables 1 and 2. The tire size was 330/710R18 for the front and 330/710R17 for the rear. In this specification, Examples 6 to 8 and 11 to 13 are reference examples.

For comparison, a tire of Conventional Example 1 having the same structure as Examples 1 to 13 except that a butyl rubber layer having no through-holes was arranged on the inner surface of the tire instead of the film layer, and a film layer having no through-holes. A tire of Conventional Example 2 having the same structure as that of Examples 1 to 13 except that it was arranged on the inner surface of the tire was prepared.

These test tires were evaluated for tire weight, steering stability, running time, and peeling resistance by the following evaluation methods. Tables 1 and 2 also show the results.

Tire weight:
Each test tire was weighed. The evaluation results are shown as index values, with Conventional Example 1 being 100, using the reciprocal of the measured value. A larger index value means a lighter weight.

Steering stability:
Each test tire was mounted on a standard rim, air pressure was adjusted to 130 kPa, mounted on a test vehicle, and sensory evaluation was performed by a test driver on a circuit. The evaluation results are shown as index values with Conventional Example 1 being 100. A larger index value means better steering stability.

Running time:
Each test tire was mounted on a standard rim and mounted on a test vehicle with an air pressure of 130 kPa. Test driving was performed on a circuit by a test driver, and the running time of 5 laps out of 7 laps excluding the first and last was measured. The evaluation results are shown as index values, with Conventional Example 1 being 100, using the reciprocal of the measured value. A larger index value means a shorter running time.

Peeling resistance:
Each test tire was mounted on a standard rim and mounted on a test vehicle at an air pressure of 130 kPa. After running for 50 minutes at an average speed of 150 km/h, the area of the portion where the film layer was peeled off was measured. The peeling resistance was evaluated only for Conventional Example 2 and Examples 1 to 13 provided with a film layer. The evaluation results are shown as indices with Conventional Example 2 set to 100 using the reciprocal of the measured value. It means that the larger the index value, the better the peeling resistance.

As is clear from Tables 1 and 2, the tires of Examples 1 to 13 were lighter in weight, had better steering stability, and had a shorter running time on the circuit, as compared with Conventional Example 1. Further, in comparison with Conventional Example 2, the tires of Examples 1 to 13 were able to prevent peeling of the film layer during running. In particular, Examples 1 to 5 exhibited good results.

REFERENCE SIGNS LIST 1 tread portion 2 side wall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 organic fiber reinforcing layer 8 belt layer 8 belt cover layer 10 inner liner layer 11 film layer 12 tie rubber layer 13 through hole

Claims (2)

A tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged inside the tire radial direction of the sidewall portions. In a pneumatic tire equipped with a A plurality of through-holes are formed in the region along the tire circumferential direction, each of the through-holes has a maximum dimension of 0.1 mm to 1.0 mm, and the through-holes form a rubber-free space. A pneumatic tire characterized by: 2. The pneumatic tire according to claim 1 , wherein the number of through-holes arranged per 100 cm ² is 1 to 400 in at least a partial area where the through-holes are formed.

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