JP6290524B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a conductive thin film rubber layer on the surface of a case.

  In recent years, the demand for lower fuel consumption of vehicles has increased, and the demand for tires with low rolling resistance has also increased. Therefore, a technique for reducing the loss tangent (tan δ) of the rubber composition constituting the tread and other members constituting the tire is widely adopted.

  As a technique for reducing the tan δ of the rubber composition, the amount of carbon black is reduced, the type of carbon black is changed, and the like. However, according to these methods, it is known that the volume specific resistance (Ω · cm) of the rubber composition is increased and the electrical conductivity of the tire is deteriorated.

  The electrical conductivity of the tire is the performance of discharging static electricity accumulated in the vehicle to the road surface. Generally, the tire is discharged through a rim, clinch, ply, sidewall, belt or breaker, and tread.

  If such a discharge is not performed, static electricity is accumulated in the vehicle, the person who gets on the vehicle gets an electric shock, sparks and fires when refueling, radio noise heard in the vehicle when driving, A trouble such as the corrosion of the rubber composition in the clinch portion is accelerated by the rim.

  As a countermeasure when the tread conductivity deteriorates due to the low tan δ of the rubber composition, there is known a technique for ensuring the electrical conductivity of the tire by adopting a base pen structure or the like (Patent Documents 1 and 2, etc.). reference.).

JP 2007-8269 A JP 2007-245918 A

  On the other hand, when the volume resistivity of the rubber composition increases due to the low tan δ of the rubber composition for the sidewall, the conductivity of the tire is ensured by ensuring the conductivity of the case disposed adjacent to the sidewall. It is necessary to suppress the deterioration of sex. Examples of a method for ensuring the conductivity of the case include a method in which the rubber composition for case topping is a rubber composition having a low volume resistivity, and the topping gauge is thickened. However, these methods have problems such as deterioration in tire rolling resistance, increase in tire weight, and increase in manufacturing cost.

  The present invention provides a predetermined thin film at a predetermined position on the inner liner side surface and / or the side wall side surface of the case, although the side wall is composed of a rubber composition for a side wall having a high volume resistivity. An object of the present invention is to provide a pneumatic tire excellent in electrical conductivity without securing conductivity in a case by having a thin rubber layer having a thickness of 0.3 mm or less composed of a rubber composition for a rubber layer. To do.

The present invention relates to a pneumatic tire having a sidewall, a breaker, a case, an inner liner, and a bead apex, wherein the sidewall has a volume resistivity of 5.0 × 10 ⁷ Ω · cm or more. A thin rubber layer having a thickness of 0.3 mm or less continuously disposed at least from the lower part of the breaker edge to the tip of the bead apex on the inner liner side surface and / or side wall side surface of the case. The thin rubber layer contains 1.7 to 3.6 parts by mass of sulfur and carbon black with respect to 100 parts by mass of the rubber component, and the DBP oil absorption value (ml / 100 g) of the carbon black and the rubber The product of the content (parts by mass) with respect to 100 parts by mass of the component is 4600 to 10,000, and the volume resistivity is 9.1 ×. A pneumatic tire which is constituted by 0 ⁸ Ω · cm or less of the thin rubber layer rubber composition.

  It is preferable that the DBP oil absorption amount of each carbon black contained in the rubber composition for a thin rubber layer is 50 to 600 ml / 100 g, and the total content with respect to 100 parts by mass of the rubber component is 30 to 60 parts by mass.

  According to the present invention, although the sidewall is made of the rubber composition for sidewall having a high volume resistivity, the predetermined amount is provided at a predetermined position on the inner liner side surface and / or the sidewall side surface of the case. By providing a thin rubber layer having a thickness of 0.3 mm or less composed of the rubber composition for a thin rubber layer, it is possible to provide a pneumatic tire with excellent electrical conductivity without securing conductivity in the case it can.

It is a fragmentary sectional view showing one mode of a pneumatic tire concerning the present invention. It is a fragmentary sectional view showing one mode of a pneumatic tire concerning the present invention.

  The pneumatic tire of the present invention is a pneumatic tire having a sidewall, a breaker, a case, an inner liner, and a bead apex.

  The sidewall is composed of a rubber composition for sidewall.

  The sidewall rubber composition is not particularly limited as long as it is a sidewall rubber composition having a reduced tan δ in order to reduce rolling resistance of a pneumatic tire.

  Examples of the technique for reducing the tan δ of the sidewall rubber composition include a technique of reducing the amount of carbon black, changing the type of carbon black, or changing both the amount and type of carbon black.

  The content of carbon black in the case of reducing the tan δ by reducing the blending amount of carbon black in the sidewall rubber composition is preferably 20 to 70 parts by mass with respect to 100 parts by mass of the rubber component, More preferably, it is 35-60 mass parts. When the content of carbon black is less than 20 parts by mass, the reinforcing effect tends to be insufficient. On the other hand, when it exceeds 70 parts by mass, the reduction of tan δ is insufficient, and the volume resistivity tends to be low.

  In the case where the sidewall rubber composition is reduced in tan δ by changing the type of carbon black, the iodine adsorption amount of carbon black is preferably 30 to 140 mg / g, and preferably 40 to 125 mg / g. Is more preferable. When the iodine adsorption amount of carbon black is less than 30 mg / g, the reinforcing effect tends to be insufficient. Moreover, when it exceeds 140 mg / g, there exists a tendency for low tan-delta formation to become inadequate. The iodine adsorption amount of carbon black is a value measured according to ASTM D1765-05.

  The tan δ of the sidewall rubber composition is preferably 0.13 or less, and more preferably 0.12 or less. When tan δ exceeds 0.13, the effect of reducing the rolling resistance of the pneumatic tire tends to be insufficient. Further, if tan δ is too low, the reinforcing property of the rubber composition tends to be lowered, and therefore it is preferably 0.08 or more.

Volume resistivity of the rubber composition for a sidewall is at 5.0 × 10 ⁷ Ω · cm or more, preferably 5.0 × 10 ⁸ Ω · cm or more, 5.0 × ¹⁰ 10 Ω · More preferably, it is cm or more. When the volume resistivity of the rubber composition is less than 5.0 × 10 ⁷ Ω · cm, the tan δ is not sufficiently lowered, and the effect of reducing the rolling resistance of the pneumatic tire tends to be insufficient. There is. Further, the upper limit of the volume resistivity is not particularly limited, but is preferably 5.0 × 10 ¹³ Ω · cm or less from the viewpoint that the reinforcing property of the rubber composition is lowered if it is too high, 5.0 × More preferably, it is 10 ¹² Ω · cm or less. In addition, the volume intrinsic low efficiency in this invention is the value measured according to JISK6271.

  A thin film rubber layer is disposed on the surface of the case constituting the pneumatic tire of the present invention. This thin film rubber layer is composed of a conductive rubber composition for a thin film rubber layer, and serves as a current-carrying path for discharging static electricity to the road surface in place of the sidewall whose conductivity has deteriorated due to the low tan δ. It is possible to improve the electrical conductivity of the entering tire.

  The thin rubber layer is disposed on the inner liner (IL) side surface and / or the side wall (SW) side surface of the case. It is preferable to be disposed only on the inner liner side surface from the viewpoint of not deteriorating the appearance of the sidewall portion, and from the point that it is possible to efficiently improve the electrical conductivity of the tire, it is disposed on the sidewall side surface. Preferably it is. Furthermore, it is more preferable that the thin rubber layer is disposed on the inner liner side surface and the side wall side surface from the viewpoint that it is possible to prevent the occurrence of poor electrical conductivity of the tire due to variations in the arrangement position of the thin film rubber layer. .

  The thin rubber layer is continuously disposed at least from the lower part of the breaker edge to the tip of the bead apex. The breaker edge and the bead apex are a breaker edge and a bead apex that are close to the same sidewall, and the bead apex tip is an end portion on the tread side of the bead apex. If the end of the thin rubber layer is not extended to the lower part of the breaker edge, the effect of improving the electrical conductivity of the tire tends to be insufficient. On the other hand, when the end of the thin film rubber layer is not extended to the tip of the bead apex, the effect of improving the conductivity tends to be insufficient.

  Here, attached FIG. 1 and FIG. 2 are partial sectional views showing an embodiment of the pneumatic tire of the present invention. FIG. 1 shows a pneumatic tire according to the present invention in which a thin rubber layer 11 is continuously disposed from a breaker edge lower part A to a bead apex C on the inner liner side surface of the case 50, and FIG. 2 shows a thin rubber layer 12. Shows a pneumatic tire according to the present invention in which the breaker edge lower part A on the side wall surface of the case 50 is continuously arranged from the bead apex tip C. A straight line p in FIGS. 1 and 2 is a straight line perpendicular to the breaker edge 31, and a case surface where the straight line p intersects is defined as a breaker edge lower part A. A straight line q in FIGS. 1 and 2 is a straight line passing through the bead apex tip 81 and parallel to the tread installation surface, and a case surface where the straight line q intersects is a bead apex tip C.

  The thin rubber layer has a thickness of 0.3 mm or less, preferably 0.2 mm or less, and more preferably 0.1 mm or less. When the thickness of the thin rubber layer exceeds 0.3 mm, the tire thickness at the portion where the thin rubber layer is disposed increases, so that the temperature rises during running of the tire and the tire durability tends to deteriorate. Further, the thickness of the thin rubber layer is 0.01 mm or more, preferably 0.05 mm or more, and more preferably 0.1 mm or more. When the thickness of the thin rubber layer is less than 0.01 mm, the effect of improving the electrical resistance of the tire tends to be insufficient.

  The width of the thin film rubber layer (the length in the tire circumferential direction) is not particularly limited. However, when the width of the thin film rubber layer is less than 1.0 mm, at least the lower part of the breaker edge continues to the tip of the bead apex. Since it becomes difficult to dispose as a layer, the thickness is preferably 1.0 mm or more.

  The thin film rubber layer can be produced by applying a rubber composition for a thin film rubber layer on the top surface of the case or the surface of the cut ply, or by attaching a rubber sheet made of the rubber composition. When the thickness of the thin rubber layer is 0.2 mm or less, it is difficult to produce a rubber sheet. Therefore, the rubber composition for the thin rubber layer is a rubber paste dissolved in an industrial solvent such as naphtha or kerosene. It is preferable to produce this by applying with a brush or the like, or spraying with a spray.

  The rubber composition for a thin film rubber layer contains a predetermined amount of sulfur and a predetermined carbon black in a rubber component.

  The rubber component is not particularly limited. Natural rubber (NR), polyisoprene rubber (IR), epoxidized natural rubber (ENR), various styrene butadiene rubbers (various SBR), and various butadienes commonly used in the rubber industry. Diene rubbers such as rubber (various BR) can be used. In particular, it is preferable to contain NR, various SBRs and various BRs from the viewpoint of excellent durability, durability and workability.

  The NR is not particularly limited, and those commonly used in the tire industry can be used. Examples thereof include SIR20, RSS # 3, and TSR20.

  The content in the case of containing NR and / or IR as a rubber component is preferably 20% by mass or more, and more preferably 30% by mass or more from the viewpoint of excellent durability and workability. NR and / or IR may be used alone, but may be used in combination with other diene rubbers. When used in combination with other diene rubbers, the content of NR and / or IR is preferably 90% by mass or less from the viewpoint of excellent reversion prevention and low heat build-up. Furthermore, 85 mass% or less is more preferable from the point that it is excellent in prevention of reversion and low heat build-up, and 80 mass% or less is further more preferable.

  The various SBRs include emulsion polymerization SBR (E-SBR) obtained by emulsion polymerization, solution polymerization SBR (S-SBR) obtained by solution polymerization, and modified SBR (modified E-SBR, modified) obtained by modifying these SBRs. S-SBR).

  The content of the various SBRs as the rubber component is preferably 10% by mass or more, and more preferably 15% by mass or more from the viewpoint of excellent durability and processability. In addition, the content of the various SBRs is preferably 60% by mass or less, and more preferably 45% by mass or less, from the viewpoint of being excellent in low heat buildup and heat deterioration resistance.

  Examples of the various BRs include high-cis 1,4-polybutadiene rubber (high-cis BR), butadiene rubber containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), and modified butadiene rubber (modified BR).

  The high cis BR is a butadiene rubber having a cis 1,4 bond content of 90% by mass or more. Examples of such high-sis BR include BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., and BR150B. By containing high cis BR, low heat build-up can be improved.

  The SPB-containing BR is not a dispersion in which 1,2-syndiotactic polybutadiene crystals are simply dispersed in BR but may be dispersed after chemically bonding with BR. Examples of such SPB-containing BR include VCR-303, VCR-412 and VCR-617 manufactured by Ube Industries.

  The modified BR is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and further the terminal of the modified BR molecule is bonded with a tin-carbon bond. Is mentioned. Examples of such a modified BR include BR1250H (tin modified) manufactured by Nippon Zeon Co., Ltd., and S modified polymer (silica modified) manufactured by Sumitomo Chemical Co., Ltd.

  Among these various BRs, high cis BRs such as BR130B and BR150B are preferably used from the viewpoint of excellent workability and durability.

  Content of the said sulfur with respect to 100 mass parts of rubber components is 1.7 mass parts or more, and it is preferable that it is 2.0 mass parts or more. When the sulfur content is less than 1.7 parts by mass, the adhesive strength with adjacent members tends to be insufficient. Moreover, content with respect to 100 mass parts of said rubber | gum rubber components is 3.6 mass parts or less, and it is preferable that it is 2.7 mass parts or less. When the sulfur content exceeds 3.6 parts by mass, the deterioration resistance of the rubber composition is lowered, which tends to be a starting point for tire destruction. In addition, the sulfur content in the present invention refers to the amount of pure sulfur component in sulfur contained as a vulcanizing agent, and does not include the sulfur component contained in the oil content, vulcanization accelerator, etc. contained in insoluble sulfur. Shall. Moreover, as sulfur, insoluble sulfur generally used in the rubber industry can be suitably used.

  The conductivity of the thin rubber layer of the present invention is greatly influenced by the content and characteristics of the carbon black contained in the rubber composition for the thin rubber layer. In the present invention, the DBP oil absorption value ( ml / 100 g) and the content (parts by mass) with respect to 100 parts by mass of the rubber component are in a predetermined range. In addition, the DBP oil absorption of carbon black in the present invention is a value measured according to JIS K 6217-4.

  The product of the DBP oil absorption value (ml / 100 g) of the carbon black and the content (parts by mass) relative to 100 parts by mass of the rubber component is 4600 or more, preferably 5175 or more. When the product of the DBP oil absorption value and the carbon black content is less than 4600, the conductivity of the thin rubber layer tends to be insufficient. Further, the product of the DBP oil absorption value and the content of the carbon black is 10,000 or less, and preferably 8000 or less. When the product of the DBP oil absorption value and the carbon black content exceeds 10,000, the viscosity of the rubber composition increases, and the processability during kneading tends to deteriorate. When two or more types of carbon black are contained, the product of the DBP oil absorption value and the carbon black content is obtained for each carbon black, and the sum of the products may satisfy the above range.

  Further, the DBP oil absorption amount of each carbon black is preferably 50 ml / 100 g or more, more preferably 70 ml / 100 g or more, and further preferably 80 ml / 100 g. When the DBP oil absorption is less than 50 ml / 100 g, the conductivity of the thin rubber layer tends to be insufficient, and when the content is increased in order to improve the conductivity, the workability during kneading tends to deteriorate. . Further, the DBP oil absorption amount of each carbon black is preferably 600 ml / 100 g or less, more preferably 500 ml / 100 g, and further preferably 440 ml / 100 g or less. When the DBP oil absorption exceeds 600 ml / 100 g, the workability during kneading tends to deteriorate, and the elongation of the vulcanized rubber composition tends to decrease and the fracture characteristics tend to deteriorate.

  The content of the carbon black with respect to 100 parts by mass of the rubber component is preferably 30 parts by mass or more, and more preferably 34 parts by mass or more. When the content of carbon black is less than 30 parts by mass, the fracture characteristics of the vulcanized rubber composition tend to be lowered, and the conductivity of the thin film rubber layer tends to be insufficient. The content of the carbon black with respect to 100 parts by mass of the rubber component is preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and further preferably 45 parts by mass or less. When the content of carbon black exceeds 60 parts by mass, the workability during kneading tends to deteriorate, and the low exothermic property of the vulcanized rubber composition tends to deteriorate. In addition, when containing 2 or more types of carbon black, the total amount of each carbon black should just satisfy the said range.

  In the rubber composition for a thin film rubber layer of the present invention, in addition to the above components, a compounding agent generally used in the production of a rubber composition, for example, a reinforcing filler such as silica, a silane coupling agent, stearic acid, Zinc oxide, various antioxidants, oils such as aroma oil, waxes, processing aids such as mixed resins, vulcanization accelerators, vulcanization accelerators, and the like can be appropriately blended.

The rubber composition for the thin film rubber layer has a volume resistivity of 9.1 × 10 ⁸ Ω · cm or less, preferably 8.2 × 10 ⁸ Ω · cm or less, and 6.2 × 10 ⁸ Ω or less. More preferably, it is cm or less. When the volume resistivity of the rubber composition exceeds 9.1 × 10 ⁸ Ω · cm, the electric conductivity of the thin rubber layer is low, and the electric conductivity of the pneumatic tire tends to be insufficient. The lower limit of the volume resistivity is not particularly limited, but is preferably 5.0 × 10 ⁶ Ω · cm or more from the viewpoint of not deteriorating the workability during kneading, and is 1.2 × 10 ⁷ Ω · cm. More preferably. In addition, the volume intrinsic low efficiency in this invention is the value measured according to JISK6271.

  The rubber composition constituting each member of the pneumatic tire breaker, case, inner liner and bead apex of the present invention is not particularly limited as long as it is generally used as a rubber composition for each member of the tire. .

The volume specific resistivity of the rubber composition constituting the breaker, case, inner liner, and bead apex is preferably 1.0 × 10 ⁸ Ω · cm or more, and 5.0. It is more preferable that it is 10 ⁸ Ω · cm or more. When the volume resistivity of these rubber compositions is less than 1.0 × 10 ⁸ Ω · cm, the effect of the present invention tends not to be sufficiently exhibited, and the rolling tire rolling resistance is reduced. Tend to be inadequate. The upper limit of the volume resistivity is not particularly limited, but is preferably 1.0 × 10 ¹⁰ Ω · cm or less from the viewpoint of securing the reinforcing performance (destructive property) of the vulcanized rubber composition.

  The pneumatic tire of the present invention is manufactured by an ordinary method using a top reaction or a cut reaction for a case having a thin film rubber layer disposed on the surface thereof. That is, the case made of the top or cut is pasted together with other tire members on a tire molding machine to mold an unvulcanized tire. The pneumatic tire of the present invention can be obtained by vulcanizing the unvulcanized tire in a vulcanizer.

  The present invention will be described based on examples, but the present invention is not limited to the examples.

The various chemicals used in the examples and comparative examples are summarized below.
NR: TSR20
SBR: JSR1502 manufactured by JSR Corporation (E-SBR, styrene content: 23.5% by mass)
BR: BR150B manufactured by Ube Industries, Ltd. (High cis BR, cis-1,4-butadiene unit amount: 97% by mass)
CB1: Show Black N220 (N220, DBP: 115 ml / 100 g, iodine adsorption amount: 119 mg / g) manufactured by Cabot Japan Co., Ltd.
CB2: Carbon Black N330 manufactured by Jiangxi Black Cat (N330, DBP: 82 ml / 100 g, iodine adsorption amount: 102 mg / g)
CB3: Printex XE2B manufactured by Evonik Degussa (DBP: 440 ml / 100 g, iodine adsorption amount: 1125 mg / g)
CB4: Show Black N550 manufactured by Cabot Japan Co., Ltd. (N550, DBP: 115 ml / 100 g, iodine adsorption amount: 44 mg / g)
Silica: ULTRASIL VN3 (BET: 175 m ² / g) manufactured by Evonik Degussa
Zinc oxide: Zinc oxide manufactured by Mitsui Kinzoku Mining Co., Ltd. Stearic acid: Stearic acid processing aid manufactured by NOF Co., Ltd. Resin mixed resin)
Oil: Vivatec 500 (TDAE oil) manufactured by H & R
Anti-aging agent 6PPD: Nocrack 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Wax: Ozoace 355 manufactured by Nippon Seiwa Co., Ltd.
Petroleum C5 Resin: ESCOREZ 1102B manufactured by ExxonMobil
Insoluble sulfur 1: Seimi OT (oil content: 10% by mass) manufactured by Nippon Kiboshi Kogyo Co., Ltd.
Insoluble sulfur 2: Mukuron OT manufactured by Shikoku Kasei Co., Ltd. (oil content: 20% by mass)
Vulcanization accelerator 1: Sunseller CM-G (N-cyclohexyl-2-benzothiazylsulfenamide) from Sanshin Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noxeller NS (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

Production Examples TF1 to TF10 (Rubber Composition for Thin Film Rubber Layer)
According to the formulation shown in Table 1, a kneaded product was obtained by kneading materials other than insoluble sulfur and vulcanization accelerators up to 180 ° C. using a 1.7 L Banbury mixer. Next, insoluble sulfur and a vulcanization accelerator were added to the kneaded product obtained, and kneaded until it reached 105 ° C. using a biaxial open roll, to obtain an unvulcanized rubber composition for a thin film rubber layer. . Further, the obtained unvulcanized rubber composition was press vulcanized for 12 minutes at 170 ° C. to obtain a vulcanized rubber composition.

Production Examples SW1 to SW3 (Rubber Composition for Side Wall)
According to the formulation shown in Table 1, a kneaded product was obtained by kneading materials other than insoluble sulfur and vulcanization accelerators up to 180 ° C. using a 1.7 L Banbury mixer. Next, insoluble sulfur and a vulcanization accelerator were added to the obtained kneaded material, and kneaded until reaching 105 ° C. using a biaxial open roll, to obtain an unvulcanized rubber composition for a sidewall. Further, the obtained unvulcanized rubber composition was press vulcanized for 12 minutes at 170 ° C. to obtain a vulcanized rubber composition.

Examples 1-12 and Comparative Examples 1-9
Each of the test tires (size: 195 / 65R15). Regarding parts other than the thin film rubber layer and the sidewall, all members formed of a rubber composition having a general composition were used in all Examples and Comparative Examples.

  In the case where the thin rubber layer is disposed, a rubber film having a thickness shown in Table 2 and Table 3 is attached to the position of the thin rubber layer shown in Table 2 and Table 3 of the case (cut ply). Test tires were prepared. In the case where the thin rubber layer is not disposed, “-” is shown in the line below “Thin rubber layer blending”.

  “A”, “B”, and “C” in “Disposition site” in Tables 2 and 3 are “breaker edge lower part A”, “buttress part B”, and “bead apex tip part C” shown in FIG. ". Further, “on the apex” indicates a position between the buttress portion B and the bead apex tip C, and “apex side” indicates a position between the tip C of the bead apex and the lower end of the bead apex. . That is, “A to apex side” indicates that the thin rubber layer is continuously disposed from A to a position between the tip C of the bead apex and the lower end of the bead apex. Further, “apex side to apex side” means that the apex side is continuously arranged from one apex side to the other apex side provided on the opposite side with respect to the tire equatorial plane.

  The following evaluation was performed using the obtained vulcanized rubber composition and the test tire.

<Volume specific resistivity>
Using a digital ultra high resistance microammeter (R-8340A) manufactured by ADVANTEST Co., Ltd., applied voltage 1000 V, temperature 23 ° C., relative humidity 55%, and other conditions according to JIS K 6271 The volume resistivity of the layer rubber composition and the side wall rubber composition was measured. The results are shown in Table 1.

<Processability during kneading>
In the production process of the rubber composition for a thin film rubber layer, workability when kneaded with a Banbury mixer was evaluated according to the following evaluation criteria. The results are shown in Table 1.
○: No burn rubber (vulcanized bit) generated ×: Yake rubber (vulcanized bit) generated

<Electric resistance of tire>
Each test tire is provided with a tread portion on an iron plate under the conditions of an internal pressure of 2.0 MPa and a load of 4.7 kN, and the electrical resistance between the rim portion and the iron plate is applied under the conditions of an applied voltage of 100 V, a temperature of 23 ° C. and a relative humidity of 55%. It was measured. In addition, the electrical resistance of the tire is 1.0 × 10 ⁸ Ω or less as a performance target value. The results are shown in Table 2 and Table 3.

<Radio noise>
Each test tire was mounted on a passenger car with a displacement of 2000 cc, and while traveling on the asphalt road surface while listening to the radio, it was confirmed whether or not radio noise (radio noise) was generated. The results are shown in Table 2 and Table 3.

<Drum durability>
Each test tire is assembled on a rim (size: 15 × 6J), filled to an internal pressure of 280 kPa, and run on a drum with a diameter of 1.7 m at a longitudinal load of 6.96 km and a speed of 80 km / h for 30000 km. Each test tire was disassembled, and it was confirmed with the naked eye whether peeling occurred at the adhesive interface between the thin rubber layer and the adjacent component. The case where peeling did not occur is indicated by ○, and the case where peeling occurred is indicated by ×. The results are shown in Table 2 and Table 3.

  From the results shown in Tables 2 and 3, the thin film rubber having a thickness of 0.3 mm or less formed of a predetermined rubber composition for a thin film rubber layer at a predetermined position on the inner liner side surface and / or side wall side surface of the case. By forming a pneumatic tire having a layer, the side wall is made of a rubber composition for a side wall having a high volume resistivity, and the conductivity is excellent without securing the conductivity in the case. It turns out that a pneumatic tire is obtained.

11, 12 Thin rubber layer 20 Tread 30 Breaker 31 Breaker edge 40 Side wall 50 Case 60 Inner liner 70 Clinch 80 Bead apex 81 Bead apex tip 90 Rim A Breaker edge lower part B Buttress part C Bead apex tip part

Claims (2)

A pneumatic tire having a sidewall, a breaker, a case, an inner liner and a bead apex,
Sidewall
It is composed of a rubber composition for a sidewall having a volume resistivity of 5.0 × 10 ¹⁰ Ω · cm or more,
On the inner liner side surface and / or sidewall side surface of the case,
A thin rubber layer having a thickness of 0.01 to 0.1 mm continuously disposed at least from the lower part of the breaker edge to the tip of the bead apex;
A thin rubber layer
Containing 1.7 to 3.6 parts by mass of sulfur and carbon black with respect to 100 parts by mass of the rubber component;
The product of the DBP oil absorption value (ml / 100 g) of carbon black and the content (parts by mass) relative to 100 parts by mass of the rubber component is 4600 to 10,000,
A pneumatic tire composed of a rubber composition for a thin film rubber layer having a volume resistivity of 9.1 × 10 ⁸ Ω · cm or less. The DBP oil absorption of each carbon black contained in the rubber composition for the thin rubber layer is 50 to 600 ml / 100 g,
The pneumatic tire according to claim 1, wherein the total content with respect to 100 parts by mass of the rubber component is 30 to 60 parts by mass.

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