JP2017218027A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which can effectively prevent vulcanization failure while satisfactorily keeping durability.SOLUTION: In a pneumatic tire which has a carcass layer 4 stretched between a pair of bead portions 3 and 3 and a belt layer 7 of at least one layer arranged on the outer peripheral side of the carcass layer 4 in a tread part 1, a first inner liner 11 composed of a first thermoplastic elastomer composition formed by dispersing an elastomer component in a thermoplastic resin containing 30 wt.% or more of high melting point polyamide having a melting point of 200°C or higher is arranged in a region that is inside of the carcass layer 4 and is in a range from at least a bead toe position and a bead filler vertex position, and a second inner liner layer 12 composed of a second thermoplastic elastomer composition formed by dispersing an elastomer component in a thermoplastic resin containing 10 wt.% or more and less than 30 wt.% of high melting point polyamide having a melting point of 200°C or higher is arranged in a region that is inside of the carcass layer 4 and is deviated from the first inner liner layer 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire having an inner liner layer made of a thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin, and more specifically, while maintaining good durability. The present invention relates to a pneumatic tire that can effectively prevent a vulcanization failure.

  In a pneumatic tire provided with a carcass layer mounted between a pair of bead portions and at least one belt layer disposed on the outer peripheral side of the carcass layer in the tread portion, air leaks inside the carcass layer. An inner liner layer carrying the prevention performance is disposed. In recent years, in order to reduce the weight of pneumatic tires, an inner liner layer made of a thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin has been proposed in place of the conventional inner liner layer mainly composed of butyl rubber. (For example, see Patent Documents 1 and 2).

  However, when the vulcanization bladder is pulled out from the inside of the vulcanized tire in the vulcanization process of the pneumatic tire provided with the inner liner layer made of the thermoplastic elastomer composition having the thermoplastic resin as a matrix as described above, There is a problem that the inner liner layer is damaged by rubbing the vulcanized bladder with the inner liner layer. That is, since the temperature of the tire immediately after vulcanization is high, the inner liner layer made of the thermoplastic elastomer composition is easily damaged particularly in the vicinity of the tire bead portion. And when an inner liner layer is damaged, the value as a tire product will fall remarkably.

  Further, by selecting a resin material having a high melting point and excellent heat resistance as the thermoplastic resin, the occurrence of the vulcanization failure as described above can be suppressed. However, when such a resin material is used, for example, since the inner liner layer becomes harder than necessary, it is difficult to satisfy the durability required for the inner liner layer.

JP 2009-241855 A JP 2009-214632 A

  An object of the present invention is to provide a pneumatic tire that can effectively prevent a vulcanization failure while maintaining good durability.

  In order to achieve the above object, a pneumatic tire according to the present invention includes a carcass layer mounted between a pair of bead portions, and at least one belt layer disposed on an outer peripheral side of the carcass layer in a tread portion. In the provided pneumatic tire, an elastomer component in a thermoplastic resin containing at least 30% by weight of a high melting point polyamide having a melting point of 200 ° C. or higher in an area from the bead toe position to the apex position of the bead filler inside the carcass layer The first inner liner layer made of the first thermoplastic elastomer composition in which is dispersed is disposed, and the melting point is 200 ° C. in a region inside the carcass layer and outside the first inner liner layer. A second elastomer component dispersed in a thermoplastic resin containing 10% by weight or more and less than 30% by weight of the above high melting point polyamide. It is characterized in that the second innerliner layer composed of a thermoplastic elastomer composition is disposed.

  In the present invention, a heat containing at least 30% by weight of a high melting point polyamide having a melting point of 200 ° C. or higher in at least a region from the bead toe position to the bead filler apex position, that is, a region where vulcanization failure is likely to occur due to rubbing of the vulcanization bladder. By disposing the first inner liner layer composed of the first thermoplastic elastomer composition in which the elastomer component is dispersed in the plastic resin, damage to the first inner liner layer in the vulcanization process is suppressed, and Sulfur failure can be effectively prevented. On the other hand, the second thermoplasticity in which the elastomer component is dispersed in the thermoplastic resin containing 10% by weight or more and less than 30% by weight of the high melting point polyamide having a melting point of 200 ° C. or higher is provided in the region outside the first inner liner layer. By arranging the second inner liner layer composed of the elastomer composition, it is possible to maintain good durability during running. By combining two types of inner liner layers with different thermoplastic resin combinations and placing them in the proper area, it is possible to effectively prevent vulcanization failures while maintaining good durability. Become.

  In the present invention, the high melting point polyamide is nylon 6 (melting point: 225 ° C.), nylon 66 (melting point: 265 ° C.), nylon 46 (melting point: 290 ° C.), nylon 610 (melting point: 225 ° C.), nylon 612 (melting point: 220 ° C.), nylon MXD6 (melting point: 237 ° C.), nylon 6T (melting point: 260 ° C.), nylon 9T (melting point: 306 ° C.), and preferably at least one selected from the group consisting of nylon 9T (melting point: 306 ° C.). Such a high melting point polyamide has a high heat resistance and thus greatly contributes to a reduction in vulcanization failure.

  The thermoplastic resin preferably contains a low melting point polyamide having a melting point of less than 200 ° C. in addition to the high melting point polyamide. Such a low-melting polyamide (particularly copolymerized polyamide) contributes to improvement in durability although it is inferior in heat resistance.

  The low melting point polyamide is selected from the group consisting of nylon 11 (melting point: 187 ° C.), nylon 12 (melting point: 176 ° C.), nylon 6/66 (melting point: 196 ° C.), nylon 6/66/12 (melting point: 188 ° C.). It is preferable that at least one selected. Such a low-melting-point polyamide exhibits good durability against repetitive strain experienced during tire running.

  The elastomer component includes halogenated isoolefin-paraalkylstyrene copolymer rubber, acid anhydride-modified ethylene-α olefin copolymer, styrene-isobutylene-styrene block copolymer, acid anhydride-modified styrene-isobutylene-styrene block copolymer. It is preferable to include at least one selected from the group consisting of a polymer and an acid anhydride-modified ethylene-ethyl acrylate copolymer. By selecting such an elastomer component, a good inner liner layer can be formed.

  The first inner liner layer and the second inner liner layer are preferably spliced together. Thus, favorable air leakage prevention performance can be ensured by arranging the first and second inner liner layers without breaks.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention.

  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. As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. As the reinforcing cord for the carcass layer 4, an organic fiber cord such as polyester is preferably used, but a steel cord may be used. A bead filler 6 made of a rubber composition having a triangular cross-section 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 include a plurality of reinforcing cords arranged so as to be inclined with respect to the tire circumferential direction, and are disposed so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °.

  For the purpose of improving high-speed durability, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 7. Yes. The belt cover layer 8 preferably has a jointless structure in which a strip material formed by aligning at least one reinforcing cord and covering with rubber is continuously wound in the tire circumferential direction. Further, the belt cover layer 8 may be disposed so as to cover the entire width direction of the belt layer 7 as illustrated, or may be disposed so as to cover only the outer edge portion of the belt layer 7 in the width direction. good. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In the pneumatic tire described above, a first inner liner layer 11 and a second inner liner layer 12 made of a thermoplastic elastomer composition are disposed on a portion inside the carcass layer 4 and facing the tire cavity. Has been.

  The first inner liner layer 11 is disposed so as to exist in at least the region X from the bead toe position to the apex position of the bead filler 6 in each of the pair of bead portions 3. An end E11 of the first inner liner layer 11 on the outer side in the tire radial direction is disposed, for example, in a region Y between the apex position of the bead filler 6 and the tire maximum width position. The first inner liner layer 11 arranged in this way is composed of a first thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 30% by weight or more of a high melting point polyamide having a melting point of 200 ° C. or higher. ing. The first inner liner layer 11 has a characteristic that heat resistance is good.

  The second inner liner layer 12 is disposed in a region away from the first inner liner layer 11. The second inner liner layer 12 arranged in this way is a second thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing a high melting point polyamide having a melting point of 200 ° C. or higher of 10% by weight or more and less than 30% by weight. It consists of things. The second inner liner layer 12 has a characteristic that it is more durable than the first inner liner layer 11.

  When manufacturing a pneumatic tire configured in this way, the carcass layer 4 mounted between the pair of bead portions 3 and 3 and at least one layer disposed on the outer peripheral side of the carcass layer 4 in the tread portion 1. A belt layer 7, and a first inner liner layer 11 is disposed at least in a region from the bead toe position to the bead filler apex position inside the carcass layer 4, and located inside the carcass layer 4 and the first A green tire in which the second inner liner layer 12 is disposed in a region deviated from the inner liner layer 11 is molded. And the green tire provided with the 1st and 2nd inner liner layers 11 and 12 is thrown in in a metal mold | die, and it vulcanizes | cures in the state which applied the internal pressure with the vulcanization bladder inserted inside the tire. And when taking out a vulcanized tire from a metal mold | die, the vulcanized bladder decompressed is pulled out from the tire inner side.

  In the pneumatic tire described above, an elastomer component in a thermoplastic resin containing 30% by weight or more of a high melting point polyamide having a melting point of 200 ° C. or higher in the region X of the bead portion 2 that easily causes vulcanization failure due to rubbing of the vulcanization bladder. By disposing the first inner liner layer 11 made of the first thermoplastic elastomer composition in which is dispersed, the damage of the first inner liner layer 11 in the vulcanization process is suppressed, and the vulcanization failure is effectively prevented. Can be prevented. On the other hand, in the region from the tread portion 1 to the side wall portion 2 where vulcanization failure due to rubbing of the vulcanization bladder is unlikely to occur, a thermoplastic containing 10% by weight or more and less than 30% by weight of a high melting point polyamide having a melting point of 200 ° C. or higher. By arranging the second inner liner layer 12 made of the second thermoplastic elastomer composition in which the elastomer component is dispersed in the resin, durability during running can be maintained well. As a result, it is possible to effectively prevent vulcanization failure while maintaining good durability.

  Here, the first inner liner layer 11 needs to be present at least in the region X from the bead toe position to the apex position of the bead filler 6, and the first inner liner layer 11 exists in the entire region X. Otherwise, the effect of preventing vulcanization failure cannot be obtained sufficiently. The end portion E11 on the outer side in the tire radial direction of the first inner liner layer 11 is desirably disposed in a region Y between the apex position of the bead filler 6 and the tire maximum width position. A vulcanization failure due to rubbing of the vulcanization bladder is relatively unlikely to occur at a position on the outer side in the tire radial direction from the maximum tire width position. On the other hand, if the first inner liner layer 11 is expanded more than necessary, the durability during traveling is lowered.

  In the pneumatic tire, the first inner liner layer 11 and the second inner liner layer 12 are spliced together. By arranging the inner liner layers 11 and 12 without breaks, good air leakage prevention performance can be ensured. In splicing the inner liner layers 11 and 12 with each other, a lap splice structure in which both ends are overlapped with each other or a butt splice structure in which both ends are abutted with each other can be employed. In the lap splice structure, both end portions may be overlapped with each other and heat-sealed.

  Hereinafter, the thermoplastic elastomer composition used in the present invention will be described. This thermoplastic elastomer composition is a composition having a structure in which a thermoplastic resin is used as a matrix and an elastomer component is dispersed in the thermoplastic resin.

  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 69 (N69), nylon 610 (N610), nylon 612 (N612), nylon 6/66 copolymer (N6 / 66), nylon 6/66/12 copolymer (N6 / 66/12), nylon 6 / 66/610 copolymer (N6 / 66/610), nylon MXD6 (MXD6), nylon 6T, nylon 6 / 6T copolymer, nylon 9T, nylon 66 / PP copolymer, nylon 66 / PPS copolymer And N-alkoxyalkylated products thereof [for example, methoxymethylated product of nylon 6, nylon 6/610 copolymer Methoxymethylated product, methoxymethylated product of nylon 612], polyester resin [for example, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET / PEI copolymer, polyarylate (PAR) , Aromatic polyesters such as polybutylene naphthalate (PBN), liquid crystal polyester, polyoxyalkylene diimide diacid / 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, Methyl methacrylate (PMMA), polyethyl methacrylate], polyvinyl resins [eg, polyvinyl acetate, polyvinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PVDC), polychlorinated Vinyl (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate copolymer, vinylidene chloride / acrylonitrile copolymer], cellulosic resin [eg, cellulose acetate, cellulose acetate butyrate], fluorine resin [ For example, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE)], imide resin [for example, aromatic polyimide (PI)] Like Can be used.

  Here, the first thermoplastic elastomer composition using a thermoplastic resin containing 30% by weight or more of a high-melting polyamide having a melting point of 200 ° C. or higher as a matrix is advantageous in reducing vulcanization failure because of its high heat resistance. If the content of the high melting point polyamide in the thermoplastic resin is less than 30% by weight, the heat resistance becomes insufficient.

  As the high melting point polyamide, at least one selected from the group consisting of nylon 6, nylon 66, nylon 46, nylon 610, nylon 612, nylon MXD6, nylon 6T, and nylon 9T may be used. Such a high melting point polyamide has a high heat resistance and thus greatly contributes to a reduction in vulcanization failure.

  The thermoplastic resin can contain a low melting point polyamide having a melting point of less than 200 ° C. in addition to the high melting point polyamide. Such a low melting point polyamide is inferior in heat resistance, but contributes to improvement in durability. The entire thermoplastic resin constituting the first thermoplastic elastomer composition may be a high melting point polyamide, but the thermoplastic elastomer contains 10% by weight to 70% by weight of a low melting point polyamide having a melting point of less than 200 ° C. It is desirable from the viewpoint of production and processing of the composition. The thermoplastic resin constituting the second thermoplastic elastomer composition preferably contains 70% by weight or more and 90% by weight or less of a low melting point polyamide having a melting point of less than 200 ° C.

  As the low melting point polyamide, at least one selected from the group consisting of nylon 11, nylon 12, nylon 6/66, and nylon 6/66/12 may be used. Such a low-melting-point polyamide exhibits good durability against repetitive strain experienced during tire running.

  Examples of the elastomer component 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 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, CI-IIR, isobutylene paramethylstyrene Polymer bromide (Br-IPMS), chloroprene rubber ( R), hydrin rubber (CHR), chlorosulfonated polyethylene rubber (CSM), chlorinated polyethylene rubber (CM), maleic acid-modified chlorinated polyethylene rubber (M-CM)], silicone rubber [eg methyl vinyl silicone rubber, dimethyl Silicone rubber, methylphenyl vinyl silicone rubber), sulfur-containing rubber (for example, polysulfide rubber), fluorine rubber (for example, vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorine-containing silicon rubber, Fluorine-containing phosphazene rubbers], thermoplastic elastomers (for example, styrene elastomers, olefin elastomers, ester elastomers, urethane elastomers, polyamide elastomers) and the like are preferably used. It kills.

  In particular, the elastomer component is a halogenated isoolefin-paraalkylstyrene copolymer rubber, an acid anhydride-modified ethylene-α olefin copolymer, a styrene-isobutylene-styrene block copolymer, an acid anhydride-modified styrene-isobutylene-styrene. It is preferable to include at least one selected from the group consisting of a block copolymer and an acid anhydride-modified ethylene-ethyl acrylate copolymer. By selecting such an elastomer component, a good inner liner layer can be formed.

  In the case where the compatibility between the specific thermoplastic resin and the elastomer described above is poor, both 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 diameter of the rubber particles forming the dispersed phase becomes finer. 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 a oxazoline group, a hydroxyl group and the like can be taken. These may be selected depending on the types of thermoplastic resin and elastomer to be mixed.

  In the present invention, thermoplastic elastomer compositions include fillers (calcium carbonate, talc, mica, titanium oxide, alumina, etc.) generally incorporated into polymer blends, reinforcing agents such as carbon black and white carbon, softening Agents, plasticizers, processing aids, pigments, dyes, anti-aging agents, and the like can be optionally added as long as the necessary properties as the inner liner layer 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 1 to 5 phr), magnesium oxide (about 4 phr), risurge (about 10 to 20 phr), p-quinonedioxime, p-dibenzoylquinonedioxime, tetrachloro-p-benzoquinone, poly- p-dinitrosobenzene (about 2 to 10 phr), methylenedianiline (about 0.2 to 10 phr), N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (0.5 to 5 phr) Degree).

  Moreover, you may add a vulcanization accelerator and a vulcanization acceleration adjuvant 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.

  Moreover, as a vulcanization | cure acceleration | stimulation adjuvant, a general rubber adjuvant can be used together, for example, zinc white (about 1-5 phr), stearic acid, oleic acid, and these Zn salts (0.5 About 4 phr).

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. Various compounding agents for the thermoplastic resin or elastomer may be added during the kneading, or may be mixed 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 100 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 adopting such a structure, the inner liner layer can be provided with sufficient flexibility and sufficient rigidity due to the effect of the resin layer as a continuous phase, and the thermoplastic resin can be molded regardless of the amount of elastomer. The same moldability as can be obtained.

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

  The thermoplastic elastomer composition can be formed into a sheet or a film and used alone, but an adhesive layer may be laminated in order to improve the adhesion to adjacent rubber. The adhesive layer may be extruded by a conventional method, for example, by a resin extruder, molded into a sheet or film, and laminated together, or coextruded with a thermoplastic resin composition or a thermoplastic elastomer composition by a resin extruder. By doing so, it may be laminated. The adhesive layer preferably contains an epoxy-modified polymer for improving adhesion. 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.

(1) Preparation of thermoplastic elastomer composition Among the raw materials shown in Table 1, rubber (Br-IPMS) was processed into a pellet shape with a rubber pelletizer (manufactured by Moriyama Seisakusho) in advance. The rubber pellets, thermoplastic resin (polyamide), acid-modified elastomer and additives (zinc oxide, stearic acid, anti-aging agent) are mixed in a twin-screw kneading extruder (manufactured by Nippon Steel Works) at the compounding ratio shown in Table 1. The mixture was added and kneaded at 250 ° C. for 3 minutes. The kneaded material was continuously extruded from an extruder into a strand shape, cooled with water, and then cut with a cutter to obtain pellet-shaped thermoplastic elastomer compositions A1 to A6.

Nylon 6/66: Novamid 2010R (nylon 6/66 copolymer) manufactured by DSM Japan Engineering Plastics Co., Ltd.
Nylon 6: manufactured by Ube Industries, UBE nylon 1011FB
Rubber: manufactured by ExxonMobil Chemical Co., brominated isobutylene-p-methylstyrene copolymer rubber, ExxproMDX89-4
Acid-modified elastomer: manufactured by Mitsui Chemicals, maleic acid-modified ethylene-butene copolymer, TAFMER MH7010
Zinc oxide: manufactured by Shodo Chemical Industry Co., Ltd., three types of zinc oxide stearic acid: manufactured by NOF Corporation, bead stearic acid 6PDD: manufactured by Flexis Co., Santoflex 6PPD

(2) Molding of film layer Each of the above-described thermoplastic elastomer compositions A1 to A6 is extruded into a tube shape at 230 ° C using an inflation molding apparatus (Placo), blown into air, and expanded with a pinch roll. By folding and winding, a tube-shaped film layer having an air permeation preventing function was obtained. The thickness of the film layer consisting of the thermoplastic elastomer compositions A1 to A6 was 60 μm. In addition, the width of each folded film layer was 650 mm.

(3) Manufacture of tires Normal tires such as a tie rubber layer, a carcass layer, a belt layer, a tread rubber layer, etc. made of unvulcanized rubber are arranged on a tire molding drum using the film layer described above as an inner liner layer. After sequentially stacking members used for manufacturing, the drum was taken out to form a green tire.

  For Examples 1 and 2, the tire structure of FIG. 1 was adopted, and the constituent materials of the first inner liner layer and the second inner liner layer were set as shown in Table 2.

  About Comparative Examples 1-6, the inner liner layer arrange | positioned over the whole region of a tire inner surface was comprised from the same raw material. In other words, the constituent material of the first inner liner layer and the constituent material of the second inner liner layer are the same as shown in Table 2.

  The green tires according to Examples 1 and 2 and Comparative Examples 1 to 6 thus obtained were vulcanized by a normal vulcanization molding method to obtain a pneumatic tire having a tire size of 195 / 65R15.

(4) Evaluation of vulcanization failure For the test tires of Examples 1 and 2 and Comparative Examples 1 to 6 manufactured as described above, the inner surface of the tire after vulcanization was visually observed, and the inner liner layer was greatly roughened. A case where there was a failure due to tearing or the like was indicated by “x”, a case where there was a failure due to minute roughness in the inner liner layer was indicated by “Δ”, and a case where there was no failure in the inner liner layer was indicated by “◯”.

(5) Evaluation of durability The test tires of Examples 1 and 2 and Comparative Examples 1 to 6 manufactured as described above were mounted on an indoor drum tester, and the air pressure was 120 kPa, the load was 4.8 kN, the speed was 80 km / h, It was made to travel 30000 km on a metal drum under the conditions of an atmospheric temperature of −20 ° C. After running, the inner surface of the tire was visually observed, and “×” indicates that the inner liner layer had defects such as cracks, and “△” indicates that the inner liner layer had slight defects such as cracks. The case where no defect was recognized in the inner liner layer was indicated by “◯”.

  As can be seen from Table 2, in Comparative Examples 1 to 3 in which the inner liner layer disposed over the entire inner surface of the tire is composed of thermoplastic elastomer compositions A1 to A3 (resin of high melting point polyamide 0% to 20%), A vulcanization failure occurred. In particular, in Comparative Example 1, a significant vulcanization failure occurs in the entire inner liner layer, in Comparative Example 2, a significant vulcanization failure occurs in the bead portion, and in Comparative Example 3, a small vulcanization failure occurs in the bead portion. It has occurred. On the other hand, in Comparative Examples 4 to 6 in which the inner liner layer disposed over the entire area of the tire inner surface is composed of the thermoplastic elastomer compositions A4 to A6 (resin of high melting point polyamide 30% to 50%), the durability is deteriorated. It was. In particular, the durability deteriorated as the blending amount of the high melting point polyamide (nylon 6) in the thermoplastic resin increased.

  On the other hand, the first inner liner layer located in the bead portion is composed of the thermoplastic elastomer composition A4 (resin made of 30% high melting point polyamide), and the second inner liner layer located in the sidewall portion from the tread portion is heated. Example 1 composed of the plastic elastomer composition A3 (resin with a high melting point polyamide 20%), and the first inner liner layer located in the bead portion is the thermoplastic elastomer composition A6 (resin with a high melting point polyamide 50%). In Example 2 in which the second inner liner layer located from the tread portion to the sidewall portion is composed of the thermoplastic elastomer composition A2 (resin of high melting point polyamide 10%), a vulcanization failure occurs. Further, the durability was good.

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 8 Belt cover layer 11 1st inner liner layer 12 2nd inner liner layer

Claims (6)

  In a pneumatic tire including a carcass layer mounted between a pair of bead portions and at least one belt layer disposed on an outer peripheral side of the carcass layer in a tread portion, the pneumatic tire has an inner side than the carcass layer. And a first thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 30% by weight or more of a high melting point polyamide having a melting point of 200 ° C. or higher at least in a region from the bead toe position to the bead filler apex position. A first inner liner layer is disposed, and a high melting point polyamide having a melting point of 200 ° C. or higher is included in an area inside the carcass layer and out of the first inner liner layer by 10 wt% or more and less than 30 wt%. Second in- stance composed of second thermoplastic elastomer composition in which elastomer component is dispersed in thermoplastic resin A pneumatic tire characterized by over liner layer is disposed.   The high-melting-point polyamide is at least one selected from the group consisting of nylon 6, nylon 66, nylon 46, nylon 610, nylon 612, nylon MXD6, nylon 6T, and nylon 9T. The described pneumatic tire.   The pneumatic tire according to claim 1 or 2, wherein the thermoplastic resin contains a low melting point polyamide having a melting point of less than 200 ° C.   The pneumatic tire according to claim 3, wherein the low-melting polyamide is at least one selected from the group consisting of nylon 11, nylon 12, nylon 6/66, and nylon 6/66/12.   The elastomer component is a halogenated isoolefin-paraalkylstyrene copolymer rubber, an acid anhydride-modified ethylene-α olefin copolymer, a styrene-isobutylene-styrene block copolymer, an acid anhydride-modified styrene-isobutylene-styrene block. The pneumatic tire according to claim 1, comprising at least one selected from the group consisting of a copolymer and an acid anhydride-modified ethylene-ethyl acrylate copolymer.   The pneumatic tire according to any one of claims 1 to 5, wherein the first inner liner layer and the second inner liner layer are spliced together.

Images