JP5082128B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that has a low rolling resistance, and that reduces the generation of static electricity during running of the tire and improves safety.

  In recent years, various methods of using silica in a tread portion, a racer, a sidewall portion, or the like of a tire have been proposed for the purpose of reducing tire rolling resistance and maintaining wet grip performance. However, when a large amount of silica is blended, the electrical resistance of the tire increases, and for example, there is a case where sparks are generated due to static electricity when the vehicle is refueled and the fuel is ignited, resulting in lack of safety during use. . Accordingly, there is a demand for providing a tire that can reduce rolling resistance and maintain wet grip performance, and can also prevent generation of static electricity.

  In Patent Document 1, as a pneumatic tire capable of improving electrical conductivity and preventing a discharge phenomenon caused by accumulation of static electricity in a vehicle body, a rubber composition constituting a tread portion has a rubber component of 100 weight. The rubber composition that contains the non-carbon black reinforcing agent in the amount of carbon black to 50 parts by weight with respect to the part and constitutes the sidewall part has a carbon black content of 100 parts by weight of the rubber component. It is 40 parts by weight or less, and the conductive thin film is disposed on the tread part and the side wall part. Here, the rubber composition constituting the conductive thin film discloses that the compounding amount of carbon black is 60% by weight or more with respect to 100 parts by weight of the rubber component and 35% by weight or more of the entire rubber composition.

Patent Document 2 discloses a pneumatic tire that effectively reduces tire electrical resistance while maintaining excellent wet performance, and that can stably exhibit these characteristics over the wear limit from the initial use of the tire. Has been proposed. Here, the tread rubber has a main tread rubber portion made of an insulating rubber material reinforced with silica and having a volume resistivity of 1 × 10 ⁸ Ω · cm or more, and a volume resistivity of less than 1 × 10 ⁸ Ω · cm. And an outer conductive portion that forms a grounding surface together with the main tread portion and terminates from the edge of the grounding surface to the inside in the tire axial direction with a distance of 3 to 35% of the grounding width. The outer conductive portion is formed in a sheet shape having a thickness of 0.01 to 1.0 mm, and is exposed on the outer surface of the tread including the groove wall of the lateral groove and the groove bottom, and is continuous in the tire circumferential direction. There has been proposed a pneumatic tire characterized in that rubber and clinch rubber are formed of a conductive rubber material, and an outer conductive portion is connected to a wing rubber.

In Patent Document 3, as a rubber composition for a tire sidewall that gives a tire having low rolling resistance, excellent wear resistance, wet performance, and low electrical resistance, the primary particle diameter is 100 parts by weight of a specific diene rubber. 5 to 50 parts by weight of carbon black having a DBP oil absorption of 120 ml / 100 g or less and a CTAB surface area of 130 m ² / g or less, a DBP oil absorption of 200 ml / 100 g or more, and a BET nitrogen adsorption specific surface area of 180 m. Rubber composition for tire sidewall obtained by kneading 10-60 parts by weight of precipitated silica of ² / g or less and an amount of silane coupling agent whose reactivity factor is controlled within a specific range Has been proposed.

Patent Document 4 discloses a strip composed of a high-resistivity rubber composition for a tire tread using silica as a reinforcing agent and having a predetermined lateral width and extending in the longitudinal direction, and a longitudinal direction within the lateral width. And a conductive strip made of a low-resistivity tire rubber composition having a volume resistivity of 10 ⁸ Ω · cm or less and extending from the surface to the bottom surface of the tread strip. A characteristic tire tread has been proposed.

However, in the methods of Patent Documents 1 to 4, there is still room for improvement in terms of achieving both a low rolling resistance and a high safety at a sufficiently satisfactory level.
JP-A-8-230407 JP 2000-190709 A JP 10-36559 A JP-A-8-34204

  The present invention effectively prevents the accumulation of static electricity generated on the tire ground contact surface or the area where the tire contacts the rim during running of the tire while keeping the rolling resistance low. And the pneumatic tire which improved the safety | security at the time of use, without impairing low-fuel-consumption property is provided.

The present invention relates to a pneumatic tire including a tread portion, a sidewall portion, a bead portion, a carcass extending from the tread portion through the sidewall portion to the bead portion, and a breaker on the outer side in the tire radial direction of the carcass. The volume specific resistances of the tread rubber, breaker rubber and sidewall rubber respectively formed on the tread portion, the breaker and the sidewall portion are 1 × 10 ⁸ Ω · cm or more, and the air The tire includes a conductive rubber disposed in a lower region at both ends of the breaker, a coated rubber that has a contact region of at least 5 mm with the conductive rubber and covers the upper side of the breaker, and is in contact with the coated rubber. The conductive rubber embedded in the tread part so that the part is exposed on the surface of the tread, Comprising a bead portion rubber disposed in a region in contact with the rim flange of the bead portion, and the volume specific resistance values of the ply rubber, the conductive rubber, the covering rubber, the energizing rubber, and the bead portion rubber constituting the carcass, All of the pneumatic tires are less than 1 × 10 ⁸ Ω · cm.

Here, the ply rubber, the conductive rubber, the covering rubber, the energizing rubber, and the bead rubber are 30 to 100 carbon black with a nitrogen adsorption specific surface area of 100 m ² / g or more with respect to 100 parts by mass of the rubber component. It is desirable to be blended in parts by mass. The bead rubber is chafer rubber or clinch rubber. Furthermore, the current-carrying rubber can be formed continuously in the tire circumferential direction.

  In the pneumatic tire of the present invention, a rubber compound having a small rolling resistance of the rubber constituting each of the tread portion, the breaker, and the sidewall portion is used, while the coated rubber on the upper side of the breaker is passed from the bead portion rubber to the sidewall portion. By electrically connecting to the current-carrying rubber embedded in the tread part so as to be in contact with the road surface, the rolling resistance of the tire is reduced, and further, it occurs on the tire ground contact surface or the region where the tire contacts the rim when the tire is running. Static electricity accumulation can be effectively prevented. As a result, it is possible to obtain a pneumatic tire with improved safety during use while maintaining the low fuel consumption of the tire.

<Basic structure>
The structure of the pneumatic tire of the present invention is exemplified in the upper right half of the tire cross section of FIG. The tire 1 includes a tread rubber 7 constituting a tread portion, a side wall rubber 8 constituting a pair of sidewall portions extending inward in the tire radial direction from both ends thereof, and a clinch located at an inner end of each sidewall portion. A clinch rubber 3 constituting the part and a chafer rubber 2 constituting the chafer located at the upper part of the rim. A carcass 10 is bridged between the clinch portion and the chafer, and a breaker rubber 9 constituting a breaker portion is disposed outside the carcass 10 in the tire radial direction. The carcass 10 is formed of one or more carcass plies on which carcass cords are arranged. The carcass ply includes a bead core 13 and a bead extending from the upper end of the bead core 13 toward the side wall through a sidewall portion. The area around the apex 11 is folded from the inner side to the outer side in the tire axial direction and is locked by the folded portion. The breaker portion is composed of two or more breaker plies in which breaker cords are arranged, and the breaker cords are stacked in different directions so that the breaker cords intersect each other. In the pneumatic tire of the present invention, the covering rubber 5 is provided between the tread portion and the breaker portion. The conductive rubber 4 is disposed between the carcass ply and both ends of the breaker part and the side wall part with a contact area of at least 5 mm with the covering rubber 5. An energizing rubber 6 is arranged in contact with the covering rubber 5 so that a part of the tread rubber 7 is exposed to the ground surface. The energizing rubber 6 is composed of the covering rubber 5, the conductive rubber 4, the carcass 10, the clinch rubber 3, and the chain. The structure is electrically connected to the fur rubber 2.

  By adopting the above structure, the bead rubber located in the contact area with the rim during running of the tire or the static electricity generated in the grounding area passes through the electrically connected conductive rubber member inside the tire and is external to the tire. To be released.

  The pneumatic tire of the present invention can be used as tires for various vehicles such as passenger cars, trucks and buses, and heavy machinery.

<Tread rubber, breaker rubber, sidewall rubber>
The volume specific resistances of the tread rubber, breaker rubber, and sidewall rubber constituting the tire are all set to 1 × 10 ⁸ Ω · cm or more. Conventionally, carbon black has been used as a rubber reinforcing agent, but rolling resistance can be reduced by replacing it with silica. Furthermore, since silica is not a petroleum-derived material, it is preferably employed from the viewpoint of environmental problems as compared with carbon, which is a petroleum-derived material. However, when silica is used, the volume resistivity tends to increase. In the present invention, the basic characteristics such as reduction of tire rolling resistance and rubber processability are maintained by using silica as a basis, while the volume resistivity of the rubber composition is as high as 1 × 10 ⁸ Ω · cm or higher. This is to improve the problem of electrical resistance.

  In the pneumatic tire of the present invention, it is preferable that 50% by mass or more of the filler contained in each of the tread rubber, the breaker rubber, and the sidewall rubber is silica. When silica accounts for 50 mass% or more of the filler, the effect of reducing the rolling resistance of the tire is good. The proportion of silica in the filler is 70% by mass or more, and more preferably 90% by mass or more. In the present invention, all of the above fillers may be silica, but other fillers are used in combination for the purpose of adjusting the electrical conductivity and mechanical strength of the tread rubber, breaker rubber and sidewall rubber. .

  Silica can be blended in an amount of, for example, 5 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the rubber component in each of the tread rubber, breaker rubber, and sidewall rubber. When the compounding amount of silica is 5 parts by mass or more with respect to 100 parts by mass of the rubber component, the rolling resistance of the tire can be reduced, and when it is 100 parts by mass or less, when manufacturing tread rubber, breaker rubber and sidewall rubber It is possible to satisfactorily prevent a decrease in processability and an excessive increase in cost due to an increase in viscosity of the unvulcanized rubber composition.

  As the silica, those generally used for general-purpose rubber can be used, and examples thereof include dry method white carbon, wet method white carbon and colloidal silica used as a reinforcing material. Among these, wet method white carbon mainly containing hydrous silicic acid is preferable.

Nitrogen adsorption specific surface area of the silica (BET method), for example 100 to 300 m ² / g, it is preferably further in the range of 150 to 250 ² / g. When the nitrogen adsorption specific surface area of silica is 100 m ² / g or more, the abrasion resistance of the tire is improved satisfactorily by obtaining a sufficient reinforcing effect. On the other hand, when the nitrogen adsorption specific surface area is 300 m ² / g or less, the processability during production of each rubber is good, and the steering stability of the tire is also ensured. The nitrogen adsorption specific surface area is measured by the BET method according to ASTM D3037-81.

<Coating rubber>
The covering rubber 5 in the present invention is made of rubber having a volume specific resistance set to less than 1 × 10 ⁸ Ω · cm, provided in contact with the conductive rubber 4 and the conductive rubber 6. If the volume resistance value is less than 1 × 10 ⁸ Ω · cm, a desired degree of improvement in tire conductivity can be obtained. The volume resistivity can be set in the same manner as the conductive rubber, and is preferably 1 × 10 ⁷ Ω · cm or less, more preferably 1 × 10 ⁶ Ω · cm or less, It is preferably 1 × 10 ³ Ω · cm or more, and more preferably 1 × 10 ⁴ Ω · cm or more.

  In the present invention, if the thickness of the covering rubber 5 is 0.2 mm or more, a desired effect of improving tire conductivity is obtained, and if it is 3.0 mm or less, the rolling resistance of the tire is not greatly deteriorated. The thickness of the conductive rubber is preferably in the range of 0.5 mm to 2.0 mm, particularly 0.9 mm to 1.5 mm. The covering rubber 5 only needs to have a portion in contact with the conductive rubber and the current-carrying rubber, and is provided over the entire surface between the tread portion and the breaker portion, or a range up to or beyond the position where the current-carrying rubber is disposed. Or can be partially provided.

  Moreover, it is preferable that the conductive rubber and the conductive rubber are in contact with the conductive rubber with a belt-shaped portion having a width of 5 mm or more in the tire circumferential direction. It is more preferable. By bringing the conductive rubber and the covering rubber into contact with each other under the above conditions, the tire conductive effect can be sufficiently obtained. The contact with the current-carrying rubber is preferably in contact with the entire surface of the current-carrying rubber in the tire width direction.

  In this invention, it is preferable that the said covering rubber contains carbon black mix | blended within the range of 30-100 mass parts with respect to 100 mass parts of a rubber component. When 30 parts by mass or more of carbon black is blended with respect to 100 parts by mass of the rubber component, the conductivity of the coated rubber is increased. Moreover, durability is improved when content of carbon black is 100 mass parts or less with respect to 100 mass parts of a rubber component. The compounding amount of carbon black with respect to 100 parts by mass of the rubber component is 35 parts by mass or more, more preferably 40 parts by mass or more, more preferably 80 parts by mass or less, and further preferably 70 parts by mass or less.

It is preferable that the nitrogen adsorption specific surface area of the carbon black compounded in the coating rubber is 100 m ² / g or more and 1500 m ² / g or less. When the nitrogen adsorption specific surface area is 100 m ² / g or more, the mechanical strength of the coated rubber is good, and when the nitrogen adsorption specific surface area is 1500 m ² / g or less, it is preferable from the viewpoint of securing the workability during production. The nitrogen adsorption specific surface area is more preferably 105 m ² / g or more, more preferably 1300 m ² / g or less, and still more preferably 1000 m ² / g or less. As the carbon black, wood tar carbon black which is a resource other than petroleum is preferably used.

  The coated rubber may contain, for example, silica or the like as a filler in addition to carbon black, but from the viewpoint of imparting good conductivity, 8% by mass or more, further 15% by mass or more of the filler, More preferably, carbon black accounts for 100% by mass.

<Conductive rubber>
In the conductive rubber 4 according to the present invention, the volume resistivity provided between the carcass ply constituting the carcass 10 described later and the edge part and the side wall part of the breaker part is set to be less than 1 × 10 ⁸ Ω · cm. Made of rubber. If the volume specific value of the conductive rubber 4 is less than 1 × 10 ⁸ Ω · cm, the effect of improving the conductivity of the tire can be obtained. The volume resistivity of the conductive rubber 4 is preferably 1 × 10 ⁷ Ω · cm or less, and more preferably set to 1 × 10 ⁶ Ω · cm or less. When a rubber composition containing a large amount of a conductive component is employed, the electrical resistance decreases, but on the other hand, the electrochemical reaction in the region where the tire is in contact with the rim is promoted and the rim is likely to rust. In order to avoid this, the volume specific resistance of the conductive rubber is preferably 1 × 10 ³ Ω · cm or more, and more preferably 1 × 10 ⁴ Ω · cm or more.

  The conductive rubber only needs to be formed continuously or discontinuously in the tire circumferential direction between the carcass ply constituting the carcass and the edge portion and side wall of the breaker portion as described above, and the thickness or shape of the conductive rubber is There is no particular limitation.

  The rubber compounding of the conductive rubber 4 can employ substantially the same compounding as the covering rubber, but adopts a composition with adjusted rubber hardness and the like from the viewpoint of reducing rubber peeling at both ends of the breaker. You can also.

<Electric rubber>
In the present invention, the current-carrying rubber is embedded in the tread portion, and a part thereof is exposed to the tire grounding surface, and the other part is connected to the conductive rubber so that the static electricity generated during the running of the pneumatic tire is effective on the grounding surface. Release. In FIG. 1, the conductive rubber 6 is shown as a structure embedded in one central portion of the tread portion 7, but a plurality of conductive rubbers can be embedded. The width W of the conductive rubber in the tire width direction is, for example, 0.2 mm to 10 mm, preferably 0.9 mm to 1.5 mm. When the width is less than 0.2 mm, the energization effect is small. On the other hand, when the width exceeds 10 mm, the grounding area of the energizing rubber in the tread portion is relatively increased, and the grounding characteristics are impaired. Moreover, although it is preferable to form the current carrying rubber as a continuous layer in the tire circumferential direction, it can also be formed intermittently in the tire circumferential direction.

The volume specific resistance of the current-carrying rubber is set lower than that of the tread rubber, breaker rubber, and sidewall rubber. Here, the volume resistivity of the conductive rubber is less than 1 × 10 ⁸ Ω · cm. When the volume specific resistance of the conductive rubber is less than 1 × 10 ⁸ Ω · cm, the conductivity of the tire is improved and the effect of discharging static electricity is obtained. The volume specific resistance of the conductive rubber is preferably 1 × 10 ⁷ Ω · cm or less, more preferably 1 × 10 ⁶ Ω · cm or less.

In the present invention, the volume specific resistance of the tread rubber, breaker rubber and sidewall rubber is set to 1 × 10 ⁸ Ω · cm or more, while maintaining the tire performance such as rolling resistance and durability, Since the volume specific resistance of the connected conductive rubber is adjusted to be lower, static electricity generated in the pneumatic tire can be effectively discharged through the electrical connection passage by the covering rubber, the conductive rubber and the current-carrying rubber. it can.

  The current-carrying rubber of the present invention can adopt the same composition as the coated rubber, but it is also possible to adopt a composition design that imparts conductivity based on the tread rubber composition from the viewpoint of improving the grounding characteristics. is there.

<Carcass>
The carcass 10 in the present invention is composed of one or more carcass plies on which carcass cords are arranged. The carcass ply has a configuration in which carcass cords are aligned in parallel and embedded in rubber. Examples of the fiber material constituting the carcass cord include rayon, nylon, polyester, and aramid. These may be used alone or in combination of two or more. Especially, since it is a natural resource material, it is preferable to use rayon, and it is preferable to mix rayon 90 mass% or more with respect to the fiber material which comprises a carcass cord.

The volume specific resistance of the ply rubber is set to be lower than that of the tread rubber, breaker rubber, and sidewall rubber. Here, the volume resistivity of the ply rubber is less than 1 × 10 ⁸ Ω · cm. When the volume specific resistance of the conductive rubber is less than 1 × 10 ⁸ Ω · cm, the conductivity of the tire is improved and the effect of discharging static electricity is obtained. The volume resistivity of the ply rubber is 1 × 10 ⁷ Ω · cm or less, and more preferably 1 × 10 ⁶ Ω · cm or less.

In the present invention, the volume specific resistance of the tread rubber, breaker rubber and sidewall rubber is set to 1 × 10 ⁸ Ω · cm or more, while maintaining tire performance such as rolling resistance and durability, Since the volume specific resistance of the covering rubber, the conductive rubber, and the conductive rubber connected to each other is adjusted to be lower, static electricity generated in the pneumatic tire is combined with the covering rubber, the conductive rubber, the conductive rubber, etc. The electrical conductivity is further improved.

  The ply rubber of the present invention can adopt the same composition as the coated rubber, but adopts a compounding design that imparts conductivity based on the compounding of the conventional ply rubber from the viewpoint of maintaining adhesion to the ply cord. It is also possible.

  Further, in the present invention, the ply is disposed so as to contact at least the clinch rubber or the chafer rubber. In addition to having a continuous structure of the conductive rubber, the covering rubber and the conductive rubber, the carcass ply having a low volume resistivity is arranged so that the clinch rubber, the chafer rubber, the conductive rubber, etc. are in contact with each other. The discharge efficiency of static electricity can be remarkably improved.

<Bead rubber>
In the present invention, “bead rubber” means clinch rubber or cheffer rubber. When the tire travels, static electricity is generated in the drive mechanism, and this static electricity is accumulated in the vehicle and also accumulated in the tire via the rim and bead rubber. Such static electricity needs to be effectively discharged to the ground plane through the conductive rubber. In FIG. 1, bead rubber, specifically clinch rubber or chafer rubber, must be electrically connected to the carcass 10. Here, the clinch rubber in FIG. 1 is a rubber layer indicated by reference numeral 3 arranged so that the outer side thereof is in contact with the rim flange and the inner side is in contact with the folded end of the carcass 10 in the tire bead portion. In FIG. 1, the chafer rubber is disposed on the outer surface of the bead portion so as to contact the flange portion from the base portion of the rim. Here, the chafer rubber 2 means a rubber constituting the chafer. That is, when the chafer is a cord ply layer, it means a cord-covered rubber, and when it is a rubber chafer, it means that rubber. The chafer rubber 2 in FIG. 1 is shown as including these concepts.

The present invention includes at least one of clinch rubber or chafer rubber as the bead rubber. Here, the volume resistivity of the bead rubber is less than 1 × 10 ⁸ Ω · cm. Good electrical conductivity of the tire can be obtained by setting the volume specific resistance of the conductive rubber to less than 1 × 10 ⁸ Ω · cm. The volume resistivity of the clinch rubber is preferably less than 1 × 10 ⁷ Ω · cm, more preferably less than 1 × 10 ⁶ Ω · cm. Since bead rubber, that is, clinch rubber and chafer rubber, is required to have wear resistance, rigidity, and hardness, the electrical resistance can be adjusted by a blending method of the conductive rubber and the current-carrying rubber in addition to the above blending design.

<Rubber compounding>
The covering rubber, conductive rubber, current-carrying rubber, ply rubber, chafer rubber, clinch rubber, tread rubber, breaker rubber, and sidewall rubber in the pneumatic tire of the present invention are composed of, for example, the following rubber compositions.

  Preferred examples of the rubber component include natural rubber (NR), epoxidized natural rubber, deproteinized natural rubber, and diene synthetic rubber. Diene-based synthetic rubbers include styrene-butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR). Butyl rubber (IIR) and the like, and rubber components containing one or more of these are preferred. The ethylene-propylene-diene rubber (EPDM) is an ethylene-propylene rubber (EPM) containing a third diene component. Examples of the third diene component include non-conjugated dienes having 5 to 20 carbon atoms such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, and 2,5-dimethyl-1,5. -Hexadiene and 1,4-octadiene, or cyclic dienes such as 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5 Examples thereof include alkenyl norbornene such as -norbornene and 2-isopropenyl-5-norbornene. In particular, dicyclopentadiene, 5-ethylidene-2-norbornene and the like are preferable.

  The rubber component used in the covering rubber, conductive rubber, energizing rubber, ply rubber, chafer rubber and clinch rubber is preferably a diene rubber, and among them, natural rubber (NR), styrene-butadiene rubber (SBR), polybutadiene rubber (BR). ), Polyisoprene rubber (IR), epoxidized natural rubber (ENR), deproteinized natural rubber and the like are preferable.

  In the rubber composition, the following compounding agents generally employed in tire rubber compounding can be appropriately compounded.

  In the present invention, as described above, silica is preferably added to the tread rubber, breaker rubber, and sidewall rubber. When silica is blended in the rubber composition, it is preferable to blend a silane coupling agent, preferably a sulfur-containing silane coupling agent, for example, in an amount of 1% by mass to 20% by mass with respect to the silica mass. By blending 1% by mass or more of the silane coupling agent, the wear resistance of the tire is improved and the rolling resistance can be reduced. On the other hand, when the compounding amount of the silane coupling agent is 20% by mass or less, there is little risk of scorching in the rubber kneading and extrusion processes.

  As sulfur-containing silane coupling agents, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethyl Examples include silylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, bis- [3- (triethoxysilyl) -propyl] tetrasulfide, 3-mercaptopropyltrimethoxysilane and the like. Other silane coupling agents include vinyltrichlorosilane, vinyltris (2-methoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ- (2-aminoethyl) Aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and the like can be used.

  In the present invention, other coupling agents such as aluminate coupling agents and titanium coupling agents can be used alone or in combination with a silane coupling agent depending on the application.

  For the rubber composition, other fillers such as carbon black, clay, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide and titanium oxide are used alone or in admixture of two or more. be able to.

  In addition to the above, a vulcanizing agent, a vulcanization accelerator, a softening agent, a plasticizer, an anti-aging agent, a foaming agent, an anti-scorch agent, and the like can be added to the rubber composition.

  As the vulcanizing agent, an organic peroxide or a sulfur vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2, 5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne- 3 or 1,3-bis (t-butylperoxypropyl) benzene, di-t-butylperoxy-diisopropylbenzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1,1- Di-t-butylperoxy-3,3,5-trimethylsiloxane, n-butyl-4, - it can be used such as di -t- butyl peroxy valerate. Of these, dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferred. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used.

  As the anti-aging agent, amine-based, phenol-based, and imidazole-based compounds, carbamic acid metal salts, waxes, and the like can be appropriately selected and used.

  In the present invention, a softener may be used in combination in order to further improve kneading processability. Softeners include process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petroleum jelly such as petroleum jelly, fatty oil softener such as castor oil, linseed oil, rapeseed oil, coconut oil, tall oil, , Waxes such as beeswax, carnauba wax and lanolin, and fatty acids such as linoleic acid, palmitic acid, stearic acid and lauric acid.

  As plasticizers, DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (phthalate) Acid diisodecyl), BBP (butylbenzyl phthalate), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate), hydrophthalic anhydride ester, DOZ (di-2-ethylhexyl azelate), DBS (dibutyl sebacate), DOS (Dioctyl sebacate), acetyl triethyl citrate, acetyl tributyl citrate, DBM (dibutyl maleate), DOM (2-ethylhexyl maleate), DBF (dibutyl fumarate) and the like.

  As the scorch preventing agent for preventing or delaying scorch, for example, organic acids such as phthalic anhydride, salicylic acid and benzoic acid, nitroso compounds such as N-nitrosodiphenylamine, N-cyclohexylthiophthalimide and the like can be used.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these.

<Bead rubber: clinch rubber, chafer rubber>
Ingredients shown in Tables 1 and 2, excluding sulfur and vulcanization accelerator, were kneaded at 150 ° C for 4 minutes using a closed Banbury mixer, and then added with sulfur and vulcanization accelerator at 95 ° C. Further kneading was conducted for 2 minutes, and bead part rubber compositions A-1, A-2, and A-3 were prepared by a conventional method.

<Preparation of ply rubber>
Ingredients shown in Table 3 excluding sulfur and vulcanization accelerator were kneaded for 4 minutes at 150 ° C. using a closed Banbury mixer, and then sulfur and vulcanization accelerator were added for 2 minutes at 95 ° C. Further, kneading was carried out to prepare ply rubber composition compositions B-1 and B-2 by a conventional method.

<Preparation of conductive rubber, coated rubber, conductive rubber>
Ingredients shown in Tables 4-6, excluding sulfur and vulcanization accelerator, were kneaded at 150 ° C. for 4 minutes using a closed Banbury mixer, and then added with sulfur and vulcanization accelerator at 95 ° C. The mixture was further kneaded for 2 minutes, and conductive rubber, coating rubber and Dentsu rubber compositions C to E were prepared by a conventional method.

<Preparation of tread rubber>
Ingredients shown in Table 7 excluding sulfur and vulcanization accelerator were kneaded at 140 ° C. for 4 minutes using a closed Banbury mixer, and sulfur and vulcanization accelerator were added for 2 minutes at 95 ° C. Further, kneading was conducted to prepare a tread rubber composition F by a conventional method.

<Preparation of side wall rubber>
The components excluding sulfur and the vulcanization accelerator shown in Table 8 were kneaded at 140 ° C. for 4 minutes using a closed Banbury mixer, and then added with sulfur and the vulcanization accelerator at 95 ° C. for 2 minutes. Further, kneading was performed to prepare sidewall rubber compositions G-1 and G-2 by a conventional method.

<Preparation of breaker rubber>
Ingredients shown in Table 9 excluding sulfur and vulcanization accelerator were kneaded at 140 ° C. for 4 minutes using a closed Banbury mixer, and sulfur and vulcanization accelerator were added for 2 minutes at 95 ° C. Further, kneading was conducted to prepare breaker rubber compositions H-1 and H-2 by a conventional method.

In Tables 1 to 9, details of the compounding agents are as follows.
Note 1: Natural rubber is trade name “TSR20” made in Thailand.
Note 2: SBR1500 is a styrene-butadiene rubber manufactured by JSR.
Note 3: SBR1502 is a styrene-butadiene rubber manufactured by JSR.
Note 4: Polybutadiene is a trade name BR150B manufactured by Ube Industries.
Note 5: N220 is carbon black manufactured by Showa Cabot Corporation (nitrogen adsorption specific surface area: 111 m ² / g, DBP oil absorption: 115 ml / 100 g).
Note 6: N330 is carbon black manufactured by Mitsubishi Chemical Corporation (nitrogen adsorption specific surface area: 79 m ² / g, DBP oil absorption: 105 ml / 100 g).
Note 7: ISAF is carbon black manufactured by Mitsubishi Chemical Corporation (nitrogen adsorption specific surface area: 115 m ² / g, DBP oil absorption: 114 ml / 100 g).
Note 8: Silica VN3 is a trade name “VN3” manufactured by Degussa. The nitrogen adsorption specific surface area is 210 m ² / g).
Note 9: Silane coupling agent is trade name “Si69” manufactured by Degussa.
Note 10: The aromatic oil is trade name X140 manufactured by Japan Energy.
Note 11: Wax is a trade name “Sannok N” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 12: The anti-aging agent is a trade name “Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.
Note 13: Stearic acid is a trade name “Stearic Acid Coffee” manufactured by NOF Corporation.
Note 14: Zinc flower is zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd.
Note 15: Sulfur is a trade name “powder sulfur” manufactured by Karuizawa Smelting Co., Ltd.
Note 16: Vulcanization accelerator 1 is a trade name “Noxeller NS-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 17: Insoluble sulfur is a trade name “Muclon OT20” manufactured by Shikoku Kasei Co., Ltd.

(Examples 1-3, Comparative Examples 1-4)
The rubber compositions prepared in Table 1 to Table 9 were used in the combinations shown in Table 10, respectively, and applied to tread parts, sidewall parts, breakers, clinch rubbers, chafer rubbers, conductive rubbers and conductive rubbers. A 195 / 65R15 pneumatic tire having the structure shown in FIG.

Here, the basic structure of the prototype tire is as follows.
Carcass ply Cord angle: 90 degrees in the tire circumferential direction Cord material: Polyester 1800 denier breaker Cord angle: 17 degrees x 17 degrees in the tire circumferential direction Cord material: Steel cord 1 x 3
In addition, the comparative example 2 is a structure which does not employ | adopt conductive rubber and electricity supply rubber | gum in the tire structure of FIG. 1, and the comparative example 3 is a structure which does not employ | adopt conductive rubber in the tire structure of FIG. Other examples and comparative examples have the same tire structure except that the rubber composition such as covering rubber, conductive rubber, and conductive rubber is different. The thickness of the covering rubber is 1 mm, the thickness of the conductive rubber is 1 mm, the width of the energizing rubber is 0.5 mm, and a continuous structure in the tire circumferential direction is employed.

<Volume resistivity>
A test piece having a thickness of 2 mm and 15 cm × 15 cm was prepared using the rubber compositions shown in Tables 1 to 9, and an electric resistance measurement R8340A manufactured by ADVANTEST was used under the conditions of voltage 500 V, temperature 25 ° C., and humidity 50%. It was measured. The results are shown in Table 1. The larger the value, the higher the volume resistivity of the rubber composition.

<Rolling resistance>
The pneumatic tire produced above was mounted on a regular rim, filled with a specified internal pressure of 200 kPa, and the rolling resistance was measured at a speed of 80 km / h and a load of 4.7 kN using a rolling resistance tester manufactured by STL. Regarding the rolling resistance coefficient (RRC) obtained by dividing the measured value of rolling resistance by the load, the value of Comparative Example 5 is set to 100, and the rolling resistances of Examples 1 to 3 and Comparative Examples 1 to 4 are shown as relative values. The smaller the value, the smaller the rolling resistance and the better the performance. The results are shown in Table 10.

<Tire conductivity>
The pneumatic tire produced above is mounted on a regular rim, filled with a specified internal pressure of 200 kPa, the tread is grounded to the iron plate with a load of 4.7 kN, and the electric resistance value between the tire rim and the iron plate at an applied voltage of 100V. Was measured. The results are shown in Table 10.

In Table 10, Comparative Example 1 uses a rubber compound with low conductivity for the ply rubber, and the conductivity of the tire is inferior. In Comparative Example 2, a rubber compound having low conductivity is used for the breaker rubber, and since no conductive rubber or conductive rubber is used, the conductivity of the tire is inferior. In Comparative Example 3, a rubber composition having high conductivity is used for the sidewall rubber, and since the conductive rubber layer is not used, the conductivity of the tire is inferior. Since Comparative Example 4 uses a rubber composition having low conductivity for the chafer rubber, the conductivity of the tire is inferior.

In Examples 1 to 3, a conductive rubber composition having a volume specific resistance of 6.1 × 10 ⁶ Ω · cm is adopted as a constituent part of a tire, while volume specific resistance of a tread portion, a breaker, and a sidewall portion is adopted. Is 1 × 10 ⁸ Ω · cm or more, so that both rolling resistance and improvement in tire conductivity can be achieved, and it can be seen that the pneumatic tire according to the present invention is excellent in both rolling resistance and conductivity.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The pneumatic tire of the present invention that can effectively release the generation of static electricity generated in a tire while traveling while maintaining a low rolling resistance is preferably applied to various vehicles such as passenger cars, trucks, buses, and heavy machinery. Can be done.

It is a figure which shows the right half of sectional drawing of the pneumatic tire which concerns on this invention.

Explanation of symbols

  1 tire, 2 chafer rubber, 3 clinch rubber, 4 conductive rubber, 5 covering rubber, 6 energizing rubber, 7 tread part, 8 sidewall part, 9 breaker, 10 carcass, 11 bead apex, 12 band, 13 bead core.

Claims (3)

A pneumatic tire including a tread portion, a sidewall portion, a bead portion, a carcass from the tread portion through the sidewall portion to the bead portion, and a breaker on the outer side in the tire radial direction of the carcass,
Volume specific resistances of the tread rubber, breaker rubber, and sidewall rubber respectively formed on the tread portion, the breaker, and the sidewall portion are 1 × 10 ⁸ Ω · cm or more,
50% by mass or more of the filler contained in each of the tread rubber, the breaker rubber, and the sidewall rubber is silica, and the nitrogen adsorption specific surface area of the silica is in the range of 150 to 250 m ² / g. Within
The pneumatic tire further includes a conductive rubber disposed in a lower region at both ends of the breaker, a coated rubber having a contact region of at least 5 mm with the conductive rubber and covering the upper side of the breaker, and in contact with the coated rubber And an electrically conductive rubber embedded in the tread portion so that a part thereof is exposed on the surface of the tread, and a bead portion rubber disposed in a region in contact with the lower end of the carcass and in contact with the rim flange of the bead portion,
The volume specific resistance values of the ply rubber, the conductive rubber, the covering rubber, the energizing rubber, and the bead rubber constituting the carcass are all less than 1 × 10 ⁸ Ω · cm, and the conductive rubber, The coating rubber, the current-carrying rubber, and the bead part rubber are blended with 100 parts by mass or less of carbon black having a nitrogen adsorption specific surface area of 100 m ² / g or more with respect to 100 parts by mass of the rubber component.
The pneumatic rubber is a pneumatic tire in which the current-carrying rubber is continuously formed in the tire circumferential direction at least in the center of the tread portion, and the width of the tire width method is 0.2 mm to 10 mm .   The pneumatic tire according to claim 1, wherein the bead rubber is a clinch rubber.   The pneumatic tire according to claim 1, wherein the bead rubber is chafer rubber.

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