JP6747071B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire provided with an inner liner layer made of a thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin inside a carcass layer, and more specifically, when a new tire and after running for a long distance are used. The present invention relates to a pneumatic tire capable of improving air leakage prevention performance in a well-balanced manner.

In a pneumatic tire including a carcass layer mounted between a pair of bead portions and at least one belt layer arranged on the outer peripheral side of the carcass layer in the tread portion, air leakage to the inside of the carcass layer An inner liner layer is provided to support the prevention performance. In recent years, in order to reduce the weight of pneumatic tires, an inner liner layer composed of a thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin is proposed instead of the conventional inner liner layer mainly composed of butyl rubber. Has been done.

Regarding a pneumatic tire having an inner liner layer made of such a thermoplastic elastomer composition, it has been proposed to blend various additives into the constituent materials of the inner liner layer in order to improve the air leakage prevention performance. (See, for example, Patent Documents 1 to 3).

However, since the fatigue of the inner liner layer in a pneumatic tire varies from tire portion to tire portion, the degree of deterioration of the air leakage prevention performance due to the fatigue varies from tire portion to tire portion. Therefore, simply devising the constituent material of the inner liner layer may locally reduce the air leakage prevention performance of the inner liner layer due to fatigue associated with long-distance running, which results in air leakage as a whole. There is a problem that the prevention performance is deteriorated.

JP2012-36244A JP, 2012-46622, A JP, 2013-166819, A

An object of the present invention is to provide a pneumatic tire capable of improving the air leakage prevention performance in a new state and after traveling a long distance in a well-balanced manner.

The pneumatic tire of the present invention for achieving the above object comprises 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. In the pneumatic tire provided, 50 parts of the ethylene-vinyl alcohol copolymer is provided inside the carcass layer and in a region having a width W1 that is 50% or more and 130% or less of the tire width direction maximum dimension WB of the belt layer. A first inner liner layer composed of a first thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing at least wt% is disposed, and the first inner liner layer is located inside the carcass layer and is the first inner layer. A second thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 70% by weight or more of polyamide in a region extending from each end of the liner layer toward the bead portion side. The inner liner layer of is arranged.

As a result of earnest research on the inner liner layer composed of a thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin, the present inventor has found that it is composed of an ethylene-vinyl alcohol copolymer (EVOH)-based thermoplastic elastomer composition. Although the inner liner layer has a high initial barrier property, the barrier property is easily deteriorated due to fatigue, and therefore the air leakage prevention performance after long-distance running tends to be low. On the other hand, from the polyamide-based thermoplastic elastomer composition The inner liner layer has a poor initial barrier property, but it has been found that deterioration of the barrier property due to fatigue is hardly seen, and the present invention has been made in view of such knowledge.

That is, in the present invention, the ethylene-vinyl alcohol copolymer weight is applied to the region of the width W1 that is 50% or more and 130% or less of the maximum tire width dimension WB of the belt layer, that is, the lower region of the belt layer that is less deformed during running. While arranging a first innerliner layer composed of a first thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 50% by weight or more of the coalescence, each end of the first innerliner layer is arranged. The elastomer component is dispersed in a thermoplastic resin containing 70% by weight or more of polyamide in a region extending from the shoulder portion to the bead portion side, that is, in a region including a shoulder portion of a tread portion which greatly deforms during traveling and a sidewall portion. By arranging the second inner liner layer composed of the second thermoplastic elastomer composition described above, a better air leakage prevention performance is ensured at the time of a new product, while the air leakage prevention performance is deteriorated due to fatigue. Since it can be minimized, it is possible to improve the air leakage prevention performance in a well-balanced manner at the time of a new article and after traveling a long distance.

In the present invention, the second inner liner layer is arranged in an area from each end of the first inner liner layer to a position within ±20 mm in the tire radial direction with reference to the bead filler apex of the bead portion. In the thermoplastic resin containing 50% by weight or more of the ethylene-vinyl alcohol copolymer in the region extending from the inner end of the second inner liner layer in the tire radial direction toward the bead portion side. A structure in which a third inner liner layer composed of a third thermoplastic elastomer composition in which an elastomer component is dispersed may be adopted. Since the peripheral region of the bead portion is also less deformed during running, it is effective to dispose the third inner liner layer made of the third thermoplastic elastomer composition in such a region. The third thermoplastic elastomer composition may be the same as the first thermoplastic elastomer composition.

The first inner liner layer and the second inner liner layer are preferably spliced with each other, and further, the second inner liner layer and the third inner liner layer are preferably spliced with each other. .. In this way, by arranging the first and second inner liner layers seamlessly or by arranging the first to third inner liner layers seamlessly, good air leakage prevention performance can be secured.

The ethylene-vinyl alcohol copolymer is preferably at least one selected from ethylene-vinyl alcohol copolymers having an ethylene content of 20 mol% to 50 mol% and modified products thereof. By selecting such an ethylene-vinyl alcohol copolymer, a good inner liner layer can be formed.

Polyamides are nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 69, nylon 610, nylon 612, nylon 6/66, nylon 6/66/12, nylon 6/66/610, nylon MXD6, nylon. It is preferably at least one selected from the group consisting of 6T, nylon 6/6T, nylon 9T and aromatic nylon. A good inner liner layer can be formed by selecting such a polyamide.

The elastomer component is a 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 contain 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.

It is a meridian sectional view showing a pneumatic tire which consists of an embodiment of the present invention. It is a meridian sectional view showing the pneumatic tire which consists of other embodiments of the present 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 according to the present embodiment includes a tread portion 1 extending in the tire circumferential direction and forming an annular shape, and a pair of sidewall portions 2 and 2 arranged on both sides of the tread portion 1. And a pair of bead portions 3, 3 arranged 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 back from the tire inner side to the outer side around a bead core 5 arranged in each bead portion 3. As the reinforcing cord of 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 arranged 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 aligned so as to be inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect 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 the range of 10° to 40°, for example.

On the outer peripheral side of the belt layer 7, 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 arranged for the purpose of improving high-speed durability. There is. It is preferable that the belt cover layer 8 has a jointless structure in which a strip material formed by aligning at least one reinforcing cord and covering it with rubber is continuously wound in the tire circumferential direction. Further, the belt cover layer 8 may be arranged so as to cover the entire area of the belt layer 7 in the width direction as illustrated, or may be arranged so as to cover only the edge portion of the belt layer 7 on the outer side 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, a first inner liner layer 11 and a second inner liner layer 12 made of a thermoplastic elastomer composition are provided at a portion inside the carcass layer 4 and facing the tire cavity. Has been done.

The first inner liner layer 11 is arranged in a region having a width W1 that is 50% or more and 130% or less of the maximum width WB of the belt layer 7 in the tire width direction. The tire width direction maximum dimension WB of the belt layer 7 means a width measured in a state where the belt layer 7 is spread on a plane, and the width W1 of the first inner liner layer 11 is a width of the inner liner layer 11 on a plane. It means the width measured in the unrolled state. Further, the widthwise center position of the first inner liner layer 11 coincides with the tire widthwise center position. The first inner liner layer 11 thus arranged is composed of a first thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 50% by weight or more of an ethylene-vinyl alcohol copolymer. There is. The first inner liner layer 11 has a characteristic that the initial barrier property is relatively high.

The second inner liner layer 12 is arranged in a region extending from each end portion E11 of the first inner liner layer 11 toward the bead portion 3 side, and the end portion E12 on the tire radial inner side is located at the bead toe position. It is located in. The second inner liner layer 12 thus arranged is composed of a second thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 70% by weight or more of polyamide. The second inner liner layer 12 has the characteristic that the deterioration of the barrier property due to fatigue is relatively small.

In the pneumatic tire described above, the first thermoplastic elastomer in which the elastomer component is dispersed in the thermoplastic resin containing 50% by weight or more of the ethylene-vinyl alcohol copolymer in the lower region of the belt layer 7 which is less likely to be deformed during running. While arranging the first inner liner layer 11 made of the composition, a thermoplastic resin containing 70% by weight or more of polyamide is provided in a region from the shoulder of the tread portion 1 which greatly deforms during running to the region including the sidewall portion 2. By disposing the second inner liner layer 12 made of the second thermoplastic elastomer composition in which the elastomer component is dispersed, it is possible to improve the air leakage prevention performance in a new state and after long-distance running with good balance.

Here, if the width W1 of the first inner liner layer 11 is smaller than 50% of the maximum width WB of the belt layer 7 in the tire width direction, the air leakage prevention performance at the time of new article cannot be sufficiently improved, and conversely from 130%. If it is too large, the performance of preventing air leakage after traveling a long distance will be deteriorated.

In the pneumatic tire, the first inner liner layer 11 and the second inner liner layer 12 are spliced to each other. By arranging the inner liner layers 11 and 12 seamlessly, good air leakage prevention performance can be secured. When the inner liner layers 11 and 12 are spliced to each other, a lap splice structure in which the ends of the inner liner layers 11 and 12 are overlapped with each other or a butt splice structure in which the ends of the two are abutted against each other can be employed. In the lap splice structure, both ends may be overlapped with each other and heat-sealed.

FIG. 2 shows a pneumatic tire according to another embodiment of the present invention. 2, the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In the pneumatic tire shown in FIG. 2, a first inner liner layer 11 and a second inner liner layer 12 made of a thermoplastic elastomer composition are provided inside the carcass layer 4 and facing the tire cavity. And a third inner liner layer 13 is provided.

The first inner liner layer 11 is arranged in a region having a width W1 that is 50% or more and 130% or less of the maximum width WB of the belt layer 7 in the tire width direction. The first inner liner layer 11 thus arranged is composed of a first thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 50% by weight or more of an ethylene-vinyl alcohol copolymer. There is. The first inner liner layer 11 has a characteristic that the initial barrier property is relatively high.

The second inner liner layer 12 is arranged in a region extending from each end portion E11 of the first inner liner layer 11 toward the bead portion 3 side, and the end portion E12 on the tire radial inner side is the bead filler 6. Is located within a range X within ±20 mm in the tire radial direction with respect to the apex of. The second inner liner layer 12 thus arranged is composed of a second thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 70% by weight or more of polyamide. The second inner liner layer 12 has the characteristic that the deterioration of the barrier property due to fatigue is relatively small.

The third inner liner layer 13 is arranged in a region extending from the end portion E12 on the inner side in the tire radial direction of the second inner liner layer 12 toward the bead portion side, and the end portion E13 on the inner side in the tire radial direction is disposed. It is located in the bead toe position. The thus arranged third inner liner layer 13 is composed of a third thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 50% by weight or more of an ethylene-vinyl alcohol copolymer. There is. The third inner liner layer 13 has the characteristic that the initial barrier property is relatively high.

In the pneumatic tire described above, the elastomer component is dispersed in the thermoplastic resin containing 50% by weight or more of the ethylene-vinyl alcohol copolymer in the lower region of the belt layer 7 and the peripheral region of the bead portion 3 which are less likely to be deformed during running. The first and third inner liner layers 11 and 13 made of the first and third thermoplastic elastomer compositions are arranged, while the shoulder portion of the tread portion 1 which is largely deformed during running and the sidewall portion 2 are included. By arranging the second inner liner layer 12 made of the second thermoplastic elastomer composition in which the elastomer component is dispersed in the thermoplastic resin containing 70% by weight or more of polyamide in the area, when the article is new and after traveling for a long distance. The air leakage prevention performance of can be improved in a balanced manner.

Here, if the width W1 of the first inner liner layer 11 is smaller than 50% of the maximum width WB of the belt layer 7 in the tire width direction, the air leakage prevention performance at the time of new article cannot be sufficiently improved, and conversely from 130%. If it is too large, the performance of preventing air leakage after traveling a long distance will be deteriorated. Moreover, when the end portion E12 on the tire radial direction inner side of the second inner liner layer 12 is located on the tire radial direction outer side from the position of 20 mm from the apex of the bead filler 6 toward the tire radial direction outer side, it follows that. Therefore, it is necessary to expand the third inner liner layer 13 to the outer side in the radial direction of the tire, so that the air leakage prevention performance after long-distance running deteriorates. On the contrary, when the end portion E12 on the tire radial direction inner side of the second inner liner layer 12 is located on the tire radial direction inner side from the position of 20 mm from the apex of the bead filler 6 toward the tire radial direction inner side, Since the occupied area of the second inner liner layer 12 becomes large, the air leakage prevention performance at the time of new article cannot be sufficiently improved.

In the pneumatic tire, the first inner liner layer 11 and the second inner liner layer 12 are spliced with each other, and the second inner liner layer 12 and the third inner liner layer 13 are spliced with each other. By arranging the inner liner layers 11 to 13 seamlessly, good air leakage prevention performance can be ensured. When the inner liner layers 11 to 13 are spliced to 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 butted against each other can be adopted. In the lap splice structure, both ends 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 ], aromatic nylon and N-alkoxyalkylated products thereof (for example, methoxymethylated product of nylon 6, methoxymethylated product of nylon 6/610 copolymer, methoxymethylated product of nylon 612), polyester resin [eg poly Butylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET/PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, polyoxyalkylene diimidic diacid/ Aromatic polyester such as polybutylene terephthalate copolymer], polynitrile resin [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, polyvinyl acetate, polyvinyl alcohol (PVA), Vinyl alcohol/ethylene copolymer (EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride/vinylidene chloride copolymer, vinylidene chloride/methyl acrylate copolymer, vinylidene chloride/acrylonitrile copolymer ], Cellulose-based resin [eg, cellulose acetate, cellulose acetate butyrate], Fluorine-based resin [eg, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene/ethylene copolymer Polymer (ETFE)], imide resin [for example, aromatic polyimide (P I)] and the like can be preferably used.

Particularly, a thermoplastic elastomer composition having a matrix of a thermoplastic resin containing 50% by weight or more of an ethylene-vinyl alcohol copolymer has a good initial barrier property. If the content of the ethylene-vinyl alcohol copolymer in the thermoplastic resin is less than 50% by weight, the improvement of the initial barrier property will be insufficient.

The ethylene-vinyl alcohol copolymer is a copolymer composed of an ethylene unit (—CH ₂ CH ₂ —) and a vinyl alcohol unit (—CH ₂ —CH(OH)—). In addition to the above, other structural units may be contained as long as the effects of the present invention are not impaired. As the ethylene-vinyl alcohol copolymer, the ethylene unit content, that is, the ethylene content is preferably 5 to 55 mol %, more preferably 20 to 50 mol %, and modified products thereof. It is preferable to use at least one selected from the above. If the ethylene content of the ethylene-vinyl alcohol copolymer is too low, the molecular chain of the ethylene-vinyl alcohol copolymer becomes rigid and the fatigue durability decreases. On the other hand, if the ethylene content is too high, the number of hydroxyl groups contained in the thermoplastic resin decreases, so that the gas permeability increases and the air barrier property decreases. The ethylene-vinyl alcohol copolymer is a saponification product of an ethylene-vinyl acetate copolymer, and the saponification degree thereof is preferably 90% or more, more preferably 99% or more. If the degree of saponification of the ethylene-vinyl alcohol copolymer is too small, the air barrier property is lowered and the thermal stability is also lowered.

The ethylene-vinyl alcohol copolymer is commercially available, and can be obtained, for example, from Nippon Synthetic Chemical Industry Co., Ltd. under the trade name of Soarnol (registered trademark) and from Kuraray Co., Ltd. under the trade name of Eval (registered trademark). it can. Examples of the ethylene-vinyl alcohol copolymer having an ethylene unit content of 5 to 55 mol% include Soarnol (registered trademark) H4815B (ethylene unit content of 48 mol%) and Soarnol (registered trademark) A4412B (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.). Ethylene unit content 42 mol%), Soarnol (registered trademark) DC3212B (ethylene unit content 32 mol%), Soarnol (registered trademark) V2504RB (ethylene unit content 25 mol%), Eval (registered trademark) manufactured by Kuraray Co., Ltd. L171B (ethylene unit content 27 mol%), Eval (registered trademark) H171B (ethylene unit content 38 mol%), Eval (registered trademark) E171B (ethylene unit content 44 mol%) and the like.

Further, the thermoplastic elastomer composition having a matrix of a thermoplastic resin containing polyamide in an amount of 70% by weight or more has good fatigue resistance, and the deterioration of the barrier property due to fatigue is relatively small. If the content of the polyamide in the thermoplastic resin is less than 70% by weight, the barrier property deteriorates due to fatigue.

As the polyamide, nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 69, nylon 610, nylon 612, nylon 6/66, nylon 6/66/12, nylon 6/66/610, nylon MXD6, At least one selected from the group consisting of nylon 6T, nylon 6/6T, nylon 9T and aromatic nylon is preferably used. A good inner liner layer can be formed by selecting such a polyamide.

Examples of the elastomer component used in the present invention include diene rubbers 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 [eg 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 [eg Br-IIR, CI-IIR, isobutylene paramethylstyrene copolymer Polymer 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 [eg, methyl vinyl silicone rubber, dimethyl silicone rubber, methylphenyl vinyl silicone rubber], sulfur-containing rubber [eg, polysulfide rubber], fluororubber [eg, vinylidene fluoride-based rubber, fluorine-containing vinyl ether-based rubber, Tetrafluoroethylene-propylene rubber, fluorine-containing silicon rubber, fluorine-containing phosphazene rubber], thermoplastic elastomer [for example, styrene elastomer, olefin elastomer, ester elastomer, urethane elastomer, polyamide elastomer] and the like are preferable. Can be used.

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 contain 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.

When the compatibility between the above-mentioned specific thermoplastic resin and the elastomer is poor, both can be compatibilized by using an appropriate compatibilizing agent as the third component. By mixing the compatibilizer in the blend system, the interfacial tension between the thermoplastic resin and the elastomer is lowered, and as a result, the diameter of the rubber particles forming the dispersed phase becomes finer, so that the characteristics of both components are better. It will be effectively expressed. Such a compatibilizer is generally a copolymer having a structure of one or both of a thermoplastic resin and an elastomer, or an epoxy group, a carbonyl group, a halogen group, an amino group capable of reacting with the thermoplastic resin or the elastomer. A copolymer having an oxazoline group, a hydroxyl group or the like can be used. These may be selected depending on the types of thermoplastic resin and elastomer to be mixed.

In the present invention, the thermoplastic elastomer composition generally includes fillers (calcium carbonate, talc, mica, titanium oxide, alumina, etc.), reinforcing agents such as carbon black, white carbon, etc., softening agents, which are commonly added to polymer blends. Agents, plasticizers, processing aids, pigments, dyes, anti-aging agents and the like can be optionally added as long as the properties required for the inner liner layer are not impaired.

The elastomer can also be dynamically vulcanized when mixed with the thermoplastic resin. The vulcanizing agent, vulcanizing aid, vulcanizing conditions (temperature, time), etc. in the case of dynamically vulcanizing 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. Specific examples of the sulfur-based vulcanizing agent include powdered sulfur, precipitable 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. ] The degree 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-butylperoxide). 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 alkylphenol resins, mixed crosslinking systems containing a halogen donor such as tin chloride and chloroprene, and an alkylphenol resin, and for example, use of about 1 to 20 phr. You can

Other than that, zinc white (about 1 to 5 phr), magnesium oxide (about 4 phr), litharge (about 10 to 20 phr), p-quinone dioxime, p-dibenzoylquinone dioxime, tetrachloro-p-benzoquinone, poly- p-dinitrosobenzene (about 2 to 10 phr), methylene dianiline (about 0.2 to 10 phr), N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (0.5 to 5 phr) Degree) can be exemplified.

Moreover, you may add a vulcanization accelerator and a vulcanization|acceleration acceleration aid as needed. Examples of the vulcanization accelerator include general vulcanization accelerators such as aldehyde/ammonia-based, guanidine-based, thiazole-based, sulfenamide-based, thiuram-based, dithioate-based, and thiourea-based compounds, for example, 0.5 to About 2 phr can be used.

As the vulcanization accelerating aid, general rubber auxiliaries can be used together, and for example, zinc white (about 1 to 5 phr), stearic acid, oleic acid and Zn salts thereof (0.5 (About 4 phr) can be used.

The method for producing the thermoplastic elastomer composition is such that a thermoplastic resin and an elastomer (unvulcanized in the case of rubber) are melt-kneaded in advance with a biaxial kneading extruder or the like to form a continuous phase (matrix). By dispersing the elastomer therein as a dispersed phase (domain). When vulcanizing the elastomer, a vulcanizing agent may be added under kneading to dynamically vulcanize the elastomer. Further, various compounding agents for the thermoplastic resin or the elastomer may be added during the above kneading, or may be mixed in advance before the 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 twin-screw kneading extruder and the like can be used. Above all, it is preferable to use a twin-screw kneading extruder for the kneading of the thermoplastic resin and the elastomer and the dynamic vulcanization of the elastomer. Further, two or more kinds of kneaders may be used and kneading may be sequentially performed. As the conditions for melt-kneading, the temperature may be equal to or higher than the temperature at which the thermoplastic resin melts. The shear rate during kneading is preferably 100 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 usual 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 the matrix of the thermoplastic resin. With such a structure, it is possible to impart sufficient flexibility to the inner liner layer and sufficient rigidity due to the effect of the resin layer as a continuous phase, and at the same time, regardless of the amount of the elastomer, a thermoplastic resin It is possible to obtain molding processability equivalent to.

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

The thermoplastic elastomer composition can be molded into a sheet or a film and used alone, but an adhesive layer may be laminated in order to enhance the adhesiveness with the adjacent rubber. The adhesive layer may be extruded by a resin extruder and formed into a sheet or a film in accordance with a conventional method to be laminated, or may be coextruded together with the thermoplastic resin composition or the thermoplastic elastomer composition by the resin extruder. You may laminate by doing. The adhesive layer preferably contains an epoxy-modified polymer in order to improve the adhesiveness. The thickness of the adhesive layer is not particularly limited, but a smaller thickness is preferable in order to reduce the weight of the tire, and a thickness of 5 μm to 150 μm is preferable.

(1) Preparation of Thermoplastic Elastomer Composition Of the raw materials shown in Table 1, rubber (Br-IPMS) was previously processed into pellets by a rubber pelletizer (manufactured by Moriyama Seisakusho). The rubber pellet, the thermoplastic resin (EVOH, polyamide), the acid-modified elastomer, and the additive (zinc oxide, stearic acid, antioxidant) are mixed at the compounding ratio shown in Table 1 in a twin-screw kneading extruder (made by Japan Steel Works). ) And kneaded at 250° C. for 3 minutes. The kneaded product was continuously extruded in a strand form from an extruder, cooled with water, and cut with a cutter to obtain pellet-shaped thermoplastic elastomer compositions A1 to A5.

EVHO: Soarnol E3808 (38 mol% ethylene) manufactured by Nippon Synthetic Chemical Industry
Polyamide: Novamid 2010R (nylon 6/66 copolymer) manufactured by DSM Japan Engineering Plastics Co., Ltd.
Rubber: Brominated isobutylene-p-methylstyrene copolymer rubber, ExxproMDX89-4 manufactured by Exxon Mobil Chemical Co.
Acid-modified elastomer: exon mobile chemical, maleic acid-modified ethylene-propylene copolymer, Exxelor VA1803
Zinc oxide: Shodo Chemical Co., Ltd., zinc oxide 3 types Stearic acid: NOF Corporation, beads stearic acid 6PDD: Flexis, Santoflex 6PPD

(2) Molding of film layer Each of the above-mentioned thermoplastic elastomer compositions A1 to A5 is extruded into a tube shape at 230° C. using an inflation molding device (manufactured by Placo), blown with air to be expanded, and then pinch roll is used. By folding and winding, a tubular film layer having an air permeation preventing function was obtained. The thickness of the film layer made of the thermoplastic elastomer compositions A1 to A5 was 100 μm. The width of each of the folded film layers was 650 mm.

(3) Manufacture of tire A normal tire such as a tie rubber layer made of unvulcanized rubber, a carcass layer, a belt layer, a tread rubber layer, or the like, is formed by disposing the above-mentioned film layer as an inner liner layer on a tire molding drum. After sequentially stacking the members used in the production, the drum was removed to form a green tire.

For Examples 1 to 6, the tire structure of FIG. 1 was adopted, and the first inner liner layer constituent material, the second inner liner layer constituent material, and the first width-wise maximum dimension WB of the belt layer relative to the first The ratio of the width W1 of the inner liner layer (W1/WB×100%) and the end position of the second inner liner layer on the radially inner side of the tire were set as shown in Table 2.

In Comparative Examples 1 and 2, the inner liner layer arranged over the entire inner surface of the tire was made of the same material. In other words, the constituent material of the first inner liner layer and the constituent material of the second inner liner layer were the same as shown in Table 2.

For Examples 7 to 9, the tire structure of FIG. 2 was adopted, and the constituent material of the first inner liner layer, the constituent material of the second inner liner layer, the constituent material of the third inner liner layer, and the belt layer. The ratio of the width W1 of the first inner liner layer to the maximum dimension WB in the tire width direction (W1/WB×100%), the end position of the second inner liner layer in the tire radial direction, and the third inner liner layer The end positions on the inner side in the tire radial direction are set as shown in Table 3. In Table 3, “bead filler apex −20 mm” means a position 20 mm inward from the bead filler apex in the tire radial direction, and “bead filler apex +20 mm” means outward from the bead filler apex in the tire radial direction. It means a position of 20 mm.

Pneumatic tires having a tire size of 195/65R15 were obtained by vulcanizing the green tires of Examples 1 to 9 and Comparative Examples 1 and 2 thus obtained by a normal vulcanization molding method.

(4) Air Leakage Test Regarding the test tires of Examples 1 to 9 and Comparative Examples 1 and 2 manufactured as described above, when used as a new tire, a FF passenger car having a displacement of 1800 cc with a rim of 15×6 JJ and an internal pressure of 200 kPa. The internal pressure drop rate of each tire after being mounted and running on an actual road for 30,000 km was measured by the following method. That is, each test tire was mounted on a regular rim, left for 3 months under an initial pressure of 250 kPa, room temperature of 21° C. and no load condition, and the internal pressure was measured every 3 hours. The measured internal pressure Pt, the initial internal pressure P0, and the elapsed days At t, Pt/P0=exp(-αt) was regressed to obtain an α value. Using the obtained α value, t=30 (day) was substituted, and the β value was calculated from β=[1-exp(−αt)]×100, and the β value was calculated as the internal pressure decrease rate per month ( %/Month). The results are shown in Tables 2 and 3, respectively.

As can be seen from Tables 2 and 3, in Comparative Example 1 in which the inner liner layer arranged over the entire inner surface of the tire was composed of the thermoplastic elastomer composition A1 (100% EVOH resin), fatigue of the inner liner layer due to running As a result, the rate of decrease in internal pressure after running was increasing, and the air leak prevention performance after running was significantly deteriorated. On the other hand, in Comparative Example 2 in which the inner liner layer arranged over the entire inner surface of the tire was made of the thermoplastic elastomer composition A4 (resin of 100% nylon), no change was observed in the internal pressure decrease rate before and after running. The rate of decrease in internal pressure at that time was slightly higher.

On the other hand, the first inner liner layer located in the lower area of the belt layer is composed of the thermoplastic elastomer compositions A1 to A3 (EVOH 50% to 100% resin), and the second inner liner layer located in the sidewall portion. In Examples 1 to 9 in which the thermoplastic elastomer compositions A4 to A5 (70% to 100% nylon resin) were used, the internal pressure drop rate when new was lower than that of Comparative Example 2, and the internal pressure after running was reduced. The reduction rate was lower than that of Comparative Example 1. As a result, the air leakage prevention performance was improved in a well-balanced state when the product was new and after traveling for a long distance.

1 Tread Part 2 Sidewall Part 3 Bead Part 4 Carcass Layer 5 Bead Core 6 Bead Filler 7 Belt Layer 8 Belt Cover Layer 11 First Inner Liner Layer 12 Second Inner Liner Layer 13 Third Inner Liner Layer

Claims (7)

In a pneumatic tire including a carcass layer mounted between a pair of bead portions and at least one belt layer arranged on the outer peripheral side of the carcass layer in the tread portion, the pneumatic tire is located inside the carcass layer. In the region of the width W1 that is 50% or more and 130% or less of the tire width direction maximum dimension WB of the belt layer, the elastomer component is dispersed in the thermoplastic resin containing 50% by weight or more of the ethylene-vinyl alcohol copolymer. A first inner liner layer composed of the thermoplastic elastomer composition of No. 1 is arranged, and extends from each end of the first inner liner layer toward the bead portion side inside the carcass layer. A second inner liner layer composed of a second thermoplastic elastomer composition in which an elastomer component is dispersed in a thermoplastic resin containing 70% by weight or more of polyamide is arranged in the region to be filled with air. Included tires. The second inner liner layer is arranged in a region from each end of the first inner liner layer to a position within ±20 mm in the tire radial direction based on the bead filler apex of the bead portion, A thermoplastic resin containing 50% by weight or more of an ethylene-vinyl alcohol copolymer in a region extending from the inner end in the tire radial direction of the second inner liner layer toward the bead portion side on the inside. The pneumatic tire according to claim 1, further comprising a third inner liner layer formed of a third thermoplastic elastomer composition in which an elastomer component is dispersed. The pneumatic tire according to claim 1, wherein the first inner liner layer and the second inner liner layer are spliced to each other. The first inner liner layer and the second inner liner layer are spliced with each other, and the second inner liner layer and the third inner liner layer are spliced with each other. The pneumatic tire according to 2. The ethylene-vinyl alcohol copolymer is at least one selected from ethylene-vinyl alcohol copolymers having an ethylene content of 20 mol% to 50 mol% and modified products thereof. Item 4. The pneumatic tire according to any one of Items 1 to 4. The polyamide is nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 69, nylon 610, nylon 612, nylon 6/66, nylon 6/66/12, nylon 6/66/610, nylon MXD6, The pneumatic tire according to any one of claims 1 to 5, which is at least one selected from the group consisting of nylon 6T, nylon 6/6T, nylon 9T, and aromatic nylon. 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, further comprising at least one selected from the group consisting of a copolymer and an acid anhydride-modified ethylene-ethyl acrylate copolymer.

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