JP2009023504A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively discharge the static electricity of a road and a tire generated during traveling, while maintaining rolling resistance low. <P>SOLUTION: In this pneumatic tire, each of the volume specific resistivity of tread rubber, breaker rubber and sidewall rubber formed on a tread, a breaker and a sidewall, respectively, is set to be 1×10<SP>8</SP>Ωcm or more. In the pneumatic tire, each of the volume specific resistivity of conduction rubber arranged between a carcass ply and the sidewall rubber and between the breaker and the tread and having a thickness of 0.2 to 3.0 mm, electro-conductive rubber connected to the conduction rubber and buried in the tread partially exposed to the surface of the tread, and a clinch connected to the lower end of the conduction rubber and arranged in a region in contact with a rim flange of a bead is lower than 1×10<SP>8</SP>Ωcm in volume specific resistance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire with reduced rolling resistance, reduced static electricity during tire running, and improved safety.

  In recent years, for the purpose of reducing tire rolling resistance and maintaining wet grip performance, various methods have been proposed in which silica is used for, for example, a tread portion of a tire, and also a breaker and a sidewall portion as another member. 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 supplying tires that can reduce rolling resistance and maintain wet grip performance, and can also prevent the 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 comprising a non-carbon black type reinforcing agent with a carbon black content of 50 parts by weight or less with respect to the part and constituting the side wall 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. Is 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 that a tire tread using silica as a reinforcing agent is composed of a rubber composition for a tire tread having a high resistivity and has a predetermined lateral width for the purpose of preventing a decrease in electrical conductivity. And a low resistivity tire having a volume resistivity of 10 ⁸ Ω · cm or less, extending in the length direction within the lateral width and extending from the surface to the bottom surface of the tread strip. A tire tread characterized by comprising a conductive strip made of a rubber composition for a vehicle 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 entered tire is further disposed between the carcass ply and the sidewall rubber constituting the carcass and between the breaker and the tread portion, and a conductive rubber having a thickness of 0.2 to 3.0 mm, and the conductive rubber A conductive rubber embedded in the tread portion so that a part thereof is exposed on the surface of the tread portion; A clinch disposed in a region connected to the lower end of the electrically conductive rubber and in contact with the rim flange of the bead portion has a volume specific resistance of less than 1 × 10 ⁸ Ω · cm of the conductive rubber, the energized rubber, and the clinch rubber. The pneumatic tire.

  In the conductive rubber, 20 to 100 parts by mass of wood tar carbon is blended with 100 parts by mass of the natural rubber component, and the conductive rubber is preferably formed continuously in the tire circumferential direction.

  In the pneumatic tire of the present invention, a material having a high electric resistance of rubber constituting each of the tread portion, the breaker, and the sidewall portion is used, while the conductive material is interposed between the carcass ply and the sidewall rubber and between the breaker and the tread portion. The conductive rubber is connected to the current-carrying rubber that is in contact with the road surface, and the electric resistance and thickness of the conductive rubber are set within a predetermined range to reduce rolling resistance. Accumulation of static electricity generated in the area in contact with the rim can be effectively prevented. As a result, it is possible to obtain a pneumatic tire with improved safety during use while maintaining low fuel consumption.

<Basic structure>
The right half of the sectional view of the pneumatic tire of the present invention is shown in FIG. In FIG. 1, a pneumatic tire T includes a tread portion 1, a breaker 2, a sidewall portion 3, and a bead portion 4, and both ends are folded back into a jointless band 8 and a pair of bead cores 5 arranged outside the breaker. A carcass 7 to be locked and a bead apex 6 extending from the upper side of the bead core 5 in the direction of the sidewall portion 3 are provided. In particular, in the present invention, the conductive rubber 9 is provided between the carcass 7 and the sidewall rubber and between the breaker 2 and the tread portion 1. And the upper end part is connected with the current-carrying rubber 11 embedded in the tread part 1 and exposed to the grounding surface, and the lower end part is connected with the clinch rubber 10 formed in the bead part 4.

  By adopting the above structure, static electricity generated in the drive mechanism during traveling of the tire and accumulated in the vehicle and inside the tire reaches the conductive rubber 11 through the conductive rubber 9 and is released to the ground plane.

  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.

(Electrical characteristics)
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, silica is preferably employed from the viewpoint of environmental problems as compared with carbon which is not a petroleum-derived material and 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 the durability of the tire and the processability of the rubber are maintained by using the silica compound as a base. On the other hand, the volume resistivity of the rubber composition is a high electric resistance of 1 × 10 ⁸ Ω · cm or more. This is to improve the problem.

(Combination)
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. It is also preferable.

  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. 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. 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 tire has good wear resistance, and when it is 100 parts by mass or less, production of 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.

Nitrogen adsorption specific surface area (BET method) of silica used in the above, 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.

<Conductive rubber>
(Construction)
In the present invention, the conductive rubber is provided between the carcass 7 and the sidewall rubber, and between the breaker 2 and the tread portion 1. The upper end portion of the conductive rubber is embedded in the tread portion 1 and connected to the exposed rubber 11 exposed to the ground surface, and the lower end portion is connected to the clinch rubber 10 formed in the bead portion 4. In FIG. 1, the conductive rubber 9 has a shape that is disposed over the entire surface of the tread portion. However, the conductive rubber 9 may be disposed only at the end portion of the tread portion. It only has to be. Moreover, it is preferable that the lower end part of the conductive rubber 9 is connected to the clinch rubber.

  In the present invention, if the thickness of the conductive rubber 9 is 0.2 mm or more, a desired effect of improving the 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.

(Electrical characteristics)
The volume specific resistance of the conductive rubber formed in the pneumatic tire of the present invention is adjusted to less than 1 × 10 ⁸ Ω · cm. When the volume resistivity of the conductive rubber is less than 1 × 10 ⁸ Ω · cm, an improvement in the conductivity of the tire is recognized. The volume resistivity of the conductive rubber is less than 1 × 10 ⁷ Ω · cm, more preferably less than 1 × 10 ⁶ Ω · cm. The volume resistivity of the conductive rubber is preferably as low as possible in terms of the effect of improving the conductivity of the tire. For example, the electrical resistance is lowered by blending a large amount of the conductive component, and the electrochemistry at the portion where the tire contacts the rim From the viewpoint of preventing the phenomenon that the reaction is accelerated and the rim is easily rusted, the volume specific resistance of the conductive rubber is set to 1 × 10 ³ Ω · cm or more, and further to 1 × 10 ⁴ Ω · cm or more. It is more preferable.

(Combination)
In this invention, it is preferable that the said conductive rubber contains carbon black mix | blended within the range of 20-100 mass parts with respect to 100 mass parts of a rubber component. When 20 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 conductive 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, and more preferably 80 parts by mass or less, and further preferably 70 parts by mass or less.

The nitrogen adsorption specific surface area of carbon black compounded in the conductive rubber is preferably 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 conductive 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.

  In addition to carbon black, the conductive rubber may contain, for example, silica as a filler, but from the viewpoint of imparting good conductivity, 8% by mass or more of the filler, further 15% by mass or more, Furthermore, it is more preferable that carbon black occupies 100 mass%.

<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 11 is shown as a structure embedded in one central portion of the tread portion 1, but a plurality of conductive rubbers can also 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 less than 1 × 10 ⁷ Ω · cm, and more preferably less than 1 × 10 ⁶ Ω · cm.

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, and while maintaining tire performance such as rolling resistance and durability, the conductive rubber and 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 conductive rubber and the conductive rubber.

  The current-carrying rubber of the present invention can adopt the same composition as the conductive 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. It is.

<Clinch rubber>
When the tire travels, driving force is transmitted from the driving mechanism via the rim and clinch rubber, and static electricity generated by the driving mechanism is accumulated in the vehicle and inside the tire. Such static electricity needs to be effectively discharged to the ground plane through the conductive rubber. In FIG. 1, the clinch rubber 10 needs to be connected to the conductive rubber 9.

Here, the volume resistivity of the clinch 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 clinch rubber requires wear resistance, rigidity, and hardness, in addition to such blending design, the electrical resistance can be adjusted by the blending technique of the conductive rubber and the current-carrying rubber.

<Rubber compounding>
The conductive rubber, current-carrying rubber, clinch rubber, tread rubber, breaker rubber, and sidewall rubber in the pneumatic tire of the present invention are composed of, for example, a rubber composition in which the following components are blended.

  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.

  Diene rubber is preferable as the rubber component used for the conductive rubber, the current-carrying rubber and the clinch rubber. 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 preferred.

  The following compounding agents generally employed in tire rubber compounding can be appropriately compounded with the rubber composition.

  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 adding a silane coupling agent, the wear resistance and steering stability of the tire can be improved. When the amount of the silane coupling agent is 1% by mass or more, the effect of improving the wear resistance and steering stability is good. Is obtained. Moreover, when the compounding quantity of a silane coupling agent is 20 mass% or less, there is little danger that the rubber | gum kneading | mixing and the baking (scorch) in an extrusion process will arise.

  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.

Here, when carbon black is blended in the tread rubber, breaker rubber, and sidewall rubber, the carbon black is preferably blended in an amount of 10 to 150 parts by mass with respect to 100 parts by mass of the rubber component. Carbon black has characteristics such as a nitrogen adsorption specific surface area (BET method) in the range of 70 to 300 m ² / g, a DBP oil absorption of 5 to 300 ml / 100 g, and an iodine adsorption of 146 to 152 mg / g. The thing in the range of raises the reinforcement effect with respect to a rubber composition. It is desirable to use wood tar carbon black which is a resource other than petroleum as carbon black.

  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, 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 (butyl benzyl phthalate), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate), hydrophthalic anhydride, 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.

<Preparation of conductive rubber and conductive rubber composition>
Ingredients shown in Table 1 excluding sulfur and vulcanization accelerator were kneaded at 150 ° 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 carried out to prepare conductive rubber and conductive rubber compositions A to C by a conventional method.

<Preparation of tread rubber composition>
Ingredients shown in Table 1 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 D by a conventional method.

<Preparation of side wall rubber composition>
Ingredients shown in Table 1 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 sidewall rubber compositions E and F by a conventional method.

<Preparation of breaker rubber composition>
Ingredients shown in Table 1 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 G and H by a conventional method.

<Preparation of clinch rubber composition>
Ingredients shown in Table 1 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 performed, and clinch rubber compositions I and J were prepared by a conventional method.

<Measurement of volume resistivity of rubber composition>
The rubber compositions A to J were measured for volume resistivity after being vulcanized and molded at 150 ° C. for 30 minutes, and the results are shown in Table 1.

Note 1: Natural rubber is trade name “TSR20” made in Thailand.
Note 2: Wood tar carbon black was produced by the oil furnace method using wood tar generated as a by-product when producing charcoal. The nitrogen adsorption specific surface area is 125 m ² / g, and the DBP oil absorption is 105 ml / 100 g.
Note 3: Silica is a trade name “VN3” manufactured by Degussa. Nitrogen adsorption specific surface area is 175 m ² / g).
Note 4: The silane coupling agent is trade name “Si69” manufactured by Degussa.
Note 5: Wax is the trade name “Sannok N” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 6: The anti-aging agent is a trade name “Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.
Note 7: Stearic acid is a trade name “Stearic Acid Coffee” manufactured by NOF Corporation.
Note 8: Zinc flower is zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd.
Note 9: Sulfur is a trade name “powder sulfur” manufactured by Karuizawa Smelting Co., Ltd.
Note 10: The vulcanization accelerator is the trade name “Noxeller NS-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 11: Sulfur is insoluble sulfur and is a trade name “Muclon OT20” manufactured by Shikoku Chemicals.

(Example 1, Comparative Examples 1-6)
Each rubber composition prepared by the above method is used in the combinations shown in Table 2, and applied to the tread part, sidewall part, breaker, clinch rubber, conductive rubber and current-carrying rubber, and vulcanized and molded by a conventional method. The structure of FIG. 1 was adopted for Example 1 and Comparative Examples 1, 2, and 6, and the structure of FIG. 2 was adopted for Comparative Examples 3 to 5 to produce pneumatic tires of size 195 / 65R15.

  The tire of FIG. 1 is formed with conductive rubber and conductive rubber, and FIG. 2 is not formed with these members. In FIG. 1, the conductive rubber has a thickness of 1.0 mm and has a structure that is continuous in the tire circumferential direction.

<Volume specific resistance>
A test piece having a thickness of 2 mm and a size of 15 cm × 15 cm was prepared using the rubber composition shown in Table 1, and measurement was performed using an electric resistance measurement R8340A manufactured by ADVANTEST under conditions of a voltage of 500 V, an air temperature of 25 ° C., and a humidity of 50%. 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. About the rolling resistance coefficient (RRC) which remove | divided the measured value of rolling resistance with the load, the value of the comparative example 1 was set to 100, and the rolling resistance of Example 1 and Comparative Examples 1-6 was shown as a relative value. As the value increases, rolling resistance increases and performance deteriorates. The results are shown in Table 2.

<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 2.

  In Table 2, since Comparative Examples 1 and 2 use a rubber composition whose volume resistivity is not sufficiently reduced as the conductive rubber, improvement in tire conductivity cannot be realized. Even when a rubber composition having a sufficiently reduced volume resistivity is used for the conductive rubber as in Comparative Example 6, if the conductivity of the clinch rubber is inferior, the conductivity of the tire is insufficient. Further, Comparative Examples 2 to 5 are based on the conventional tire structure (FIG. 2), Comparative Example 3 has poor conductivity, and Comparative Examples 4 and 5 have insufficient rolling resistance.

In contrast, a conductive rubber having a volume resistivity of 6.1 × 10 ⁶ Ω · cm is formed, and the volume resistivity of the tread portion, breaker, and sidewall portion is set to 1 × 10 ⁸ Ω · cm or more. In Example 1, rolling resistance and tire conductivity are highly compatible, 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. It is a figure which shows the right half of sectional drawing of the conventional pneumatic tire.

Explanation of symbols

  T tire, 1 tread part, 2 breaker, 3 side wall part, 4 bead part, 5 bead core, 6 bead apex, 7 carcass, 8 band, 9 conductive rubber, 10 clinch rubber, 11 energizing rubber.

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 a tire radial outside 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,
The pneumatic tire is further disposed between a carcass ply and the sidewall rubber constituting the carcass and between a breaker and a tread portion, and a conductive rubber having a thickness of 0.2 to 3.0 mm. A rubber that is connected to the rubber and is embedded in the tread so that a part of the rubber is exposed on the surface of the tread, and a clinch that is connected to the lower end of the conductive rubber and is in contact with the rim flange of the bead. Prepared,
A pneumatic tire in which the conductive rubber, the conductive rubber, and the clinch rubber have a volume specific resistance of less than 1 × 10 ⁸ Ω · cm.   2. The pneumatic tire according to claim 1, wherein the conductive rubber contains 20 to 100 parts by mass of wood tar carbon black with respect to 100 parts by mass of a natural rubber component.   The pneumatic tire according to claim 1, wherein the conductive rubber is formed continuously in a tire circumferential direction.

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