JP2014051216A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire in which a tread and a side wall are composed of a rubber composition having a high volume specific resistivity and which has excellent conductivity and rolling resistance characteristics even though it has no insulation having high conductivity.SOLUTION: In a pneumatic tire which has a tread and a side wall composed of a rubber composition having a predetermined volume specific resistivity and has no insulation having high conductivity, there can be provided a pneumatic tire having excellent conductivity and rolling resistance characteristics by forming a diamond-like carbon thin film having a film thickness of 1 to 10 μm on an outer surface of the side wall.

Description

  The present invention relates to a pneumatic tire having a diamond-like carbon thin film on an outer surface of a sidewall.

  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. In view of this, a technique for reducing the loss tangent (tan δ) of a rubber composition that constitutes a member constituting a tire such as a tread or a sidewall 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, 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 rimmed rim.

  Therefore, as means for improving the electrical conductivity of the tire, a tire having a base pen structure with a high conductivity in the tire crown (see Patent Documents 1 and 2, etc.) and an installation with a high conductivity are provided. Proposed to be tires. However, these means have a problem that the tire weight is increased and the productivity is deteriorated by arranging a new part. Further, since a rubber composition having a low volume resistivity and a high tan δ is used as the base pen and the insulation, there is room for improvement in rolling resistance characteristics.

  On the other hand, Patent Literature 3 describes that a pneumatic tire excellent in internal pressure retention is formed by forming a carbon film made of diamond-like carbon (DLC) or the like on the tire cavity surface. However, no consideration is given to the formation of the carbon film at a predetermined position on the outer surface of the tire and the improvement of the conductivity by the diamond-like carbon film.

JP 2007-8269 A JP 2007-245918 A JP 2006-69326 A

  In the present invention, the tread and the sidewall are made of a rubber composition having a high volume resistivity, and further, although having a predetermined diamond-like carbon thin film despite having no insulation with high conductivity, An object of the present invention is to provide a pneumatic tire excellent in electric conductivity and rolling resistance characteristics.

The present invention relates to a tread composed of a rubber composition for tread having a volume resistivity of 1.0 × 10 ^{9 to} 1.0 × 10 ¹³ Ω · cm, and
Having a sidewall composed of a rubber composition for sidewall having a volume resistivity of 1.0 × 10 ^{9 to} 1.0 × 10 ¹³ Ω · cm;
It is a pneumatic tire having no insulation composed of a rubber composition for insulation having a volume resistivity of 1.0 × 10 ⁸ Ω · cm or less,
The present invention relates to a pneumatic tire having a diamond-like carbon thin film with a film thickness of 1 to 10 μm formed on a sidewall outer surface by a plasma CVD method.

  The diamond-like carbon thin film is preferably formed continuously from the shoulder portion of the pneumatic tire to the bead portion.

  According to the present invention, the tread and the sidewall are made of a rubber composition having a high volume resistivity, and the film thickness is 1 on the outer surface of the sidewall despite having no insulation with a high conductivity. By forming a diamond-like carbon thin film of 10 μm, it is possible to provide a pneumatic tire excellent in electrical conductivity and rolling resistance characteristics.

It is the schematic which shows the partial cross section of one form of the pneumatic tire which concerns on this invention.

  The pneumatic tire of the present invention has a tread composed of a predetermined rubber composition for a tread and a sidewall composed of a predetermined rubber composition for a sidewall, and has a predetermined film thickness on an outer surface of the sidewall. A diamond-like carbon (DLC) thin film.

  The rubber composition for a tread and the rubber composition for a sidewall are rubber compositions that have been reduced in tan δ in order to reduce rolling resistance of a pneumatic tire, and have a specific volume resistivity within a predetermined range. If it is a thing, it will not specifically limit, The rubber composition for treads and the rubber composition for sidewalls which are used for the conventional pneumatic tire can be used.

The volume resistivity of the rubber composition for tread is 1.0 × 10 ⁹ Ω · cm or more, preferably 1.0 × 10 ¹⁰ Ω · cm or more, and more preferably 1.0 × 10 ¹¹ Ω · cm or more. preferable. When the volume resistivity of the rubber composition is less than 1.0 × 10 ⁹ 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. . Further, the upper limit of the volume resistivity is 1.0 × 10 ¹³ Ω · cm or less, preferably 1.0 × 10 ¹² Ω · cm or less from the viewpoint that the reinforcing property of the rubber composition is lowered when it is too high. . In addition, the volume resistivity in the present invention is a value measured according to JIS K 6271.

  Further, the tan δ of the tread rubber composition is preferably 0.50 or less, and more preferably 0.30 or less. When tan δ exceeds 0.50, 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, so 0.20 or more is preferable. In the present invention, tan δ of the rubber composition for a tread is a value obtained by measuring viscoelastic properties under conditions of an initial strain of 10%, a dynamic strain of 2%, a vibration frequency of 10 Hz, and a temperature of 30 ° C. The same applies to the rubber composition for sidewalls described later.

The volume resistivity of the rubber composition for sidewalls is 1.0 × 10 ⁹ Ω · cm or more, preferably 1.0 × 10 ¹⁰ Ω · cm or more, and 1.0 × 10 ¹¹ Ω · cm or more. Further preferred. When the volume resistivity of the rubber composition is less than 1.0 × 10 ⁹ 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. . Further, the upper limit of the volume resistivity is 1.0 × 10 ¹³ Ω · cm or less, preferably 1.0 × 10 ¹² Ω · cm or less from the viewpoint that the reinforcing property of the rubber composition is lowered when it is too high. .

  Further, tan δ of the rubber composition for a sidewall is preferably 0.50 or less, and more preferably 0.30 or less. When tan δ exceeds 0.50, 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, so 0.20 or more is preferable.

  As a method for reducing the tan δ of the rubber composition for tread and the rubber composition for sidewall, the amount of carbon black is reduced, the type of carbon black is adjusted, and both the amount and type of carbon black are adjusted. Or a technique.

  The content of carbon black in the tread rubber composition is preferably 15 to 30 parts by mass, and more preferably 20 to 25 parts by mass with respect to 100 parts by mass of the rubber component. When the content of carbon black is less than 15 parts by mass, it is difficult to obtain the effect as a reinforcing agent, and wear resistance and hardness tend to decrease. Moreover, when it exceeds 30 mass parts, tan-delta reduction is inadequate and there exists a tendency for the volume resistivity of a rubber composition to become low.

  Moreover, 15-30 mass parts is preferable with respect to 100 mass parts of rubber components, and, as for content of carbon black in the rubber composition for sidewalls, 20-25 mass parts is more preferable. When the content of carbon black is less than 15 parts by mass, it is difficult to obtain the effect as a reinforcing agent, and wear resistance and hardness tend to decrease. Moreover, when it exceeds 30 mass parts, tan-delta reduction is inadequate and there exists a tendency for the volume resistivity of a rubber composition to become low.

The pneumatic tire of the present invention is a pneumatic tire that does not have an installation with a high electrical conductivity and is composed of a rubber composition for insulation having a volume resistivity of 1.0 × 10 ⁸ Ω · cm or less. Insulation with high electrical conductivity is a member arranged to improve the electrical conductivity of the tire, and is composed of a rubber composition having a low volume resistivity and a high tan δ. As a result, the rolling resistance characteristics tend to deteriorate. The pneumatic tire of the present invention has improved rolling resistance characteristics by not having an insulation with high electrical conductivity, and succeeded in improving the electrical conductivity of the pneumatic tire by a diamond-like carbon thin film described later. In addition, in the case of an insulation composed of a rubber composition for insulation having a volume resistivity exceeding 1.0 × 10 ⁸ Ω · cm, the rolling resistance characteristics are not easily lowered even if disposed, but the tire weight From the viewpoint of reducing the production efficiency and reducing the production efficiency due to the installation of the insulation, it is preferable not to have the insulation regardless of the volume resistivity of the rubber composition for the insulation.

  The pneumatic tire of the present invention has a diamond-like carbon (DLC) thin film on the sidewall outer surface. The DLC thin film has excellent electrical conductivity, and has a low tan δ, and instead of treads and sidewalls that are not highly conductive, it becomes a current-carrying path for discharging static electricity to the road surface. Can be improved. Moreover, the effect which protects the rubber | gum of the tire outer surface is also acquired, and the discoloration of the rubber | gum by deterioration can also be suppressed.

  The DLC thin film is formed on a sidewall outer surface of a vulcanized pneumatic tire by a plasma CVD method. By forming by a plasma CVD method, a uniform thin film can be formed at a desired position.

  Formation of the DLC thin film by the plasma CVD method is performed by converting a hydrocarbon gas as a raw material into plasma and evaporating it on the target surface (the outer surface of the tire). The plasma CVD method is not particularly limited, and examples thereof include a thermal CVD method, a hot filament CVD method, an electron impact CVD method, a thermal plasma CVD method, a low temperature plasma CVD method, and the low temperature plasma CVD method includes an RF plasma CVD method, Examples include microwave plasma CVD, ECR (Electron Cyclotron Resonance) -plasma CVD, and the like. Of these, the low-temperature plasma CVD method is preferable because a DLC thin film can be formed in a low-temperature environment. Examples of the raw material hydrocarbon include methane, ethane, acetylene, propane, butane, benzene, toluene and the like.

  The formation position of the DLC thin film will be described with reference to FIG. FIG. 1 is a schematic view showing a partial cross section of an embodiment of the pneumatic tire of the present invention. The DLC thin film 10 extends from the shoulder portion S to the outer surface of the wing 22, the outer surface of the sidewall 21, and the outer surface of the clinch 23. A pneumatic tire formed up to the bead part B is shown.

  The DLC thin film of the present invention is formed on the outer surface of the sidewall.

  The front end portion of the DLC thin film on the tire contact surface side (tread side) is preferably extended to the shoulder portion S that contacts the road surface during traveling from the viewpoint that static electricity can be efficiently discharged to the road surface. Moreover, when the wing 22 is a wing having high conductivity, the road surface can be energized through the wing by being formed up to a position in contact with the wing.

  On the other hand, the tip on the rim side is preferably formed up to a position in contact with the rim, more preferably up to the bead portion B, from the viewpoint that the static electricity generated in the vehicle can be easily received from the rim. In addition, when the clinch 23 is a clinch having high conductivity, it is possible to receive static electricity from the rim through the clinch because the clinch 23 is formed up to a position in contact with the clinch.

When the wing having a high conductivity and / or the clinch having a high conductivity are used, the volume resistivity of the rubber composition constituting these parts is preferably 1.0 × 10 ⁶ Ω · cm or less, and 1.0 × 10 ⁵ Ω · cm or less is more preferable, and 1.0 × 10 ⁴ Ω · cm or less is more preferable. When the volume resistivity exceeds 1.0 × 10 ⁶ Ω · cm, the electrical conductivity is low, and the electric conductivity of the tire tends to be insufficient.

  The film thickness of the DLC thin film is 1 μm or more, preferably 4 μm or more. When the film thickness is less than 1 μm, it tends to be difficult to form a thin film and the conductivity is insufficient. Moreover, the film thickness of a DLC thin film is 10 micrometers or less, and 6 micrometers or less are preferable. When the film thickness exceeds 10 μm, it is difficult to follow the elastic deformation of the tire when traveling on the road surface, and the DLC thin film tends to peel off. In addition, the film thickness of the DLC thin film in this invention shall be the value measured by the X-ray reflectivity method (XRR method).

  The width of the thin rubber layer (the length in the tire circumferential direction) is not particularly limited, but it is preferable that the thin rubber layer has a width of 10 mm or more from the viewpoint of preventing peeling due to external contact or elastic deformation, More preferably formed uniformly on the tire circumference

  The pneumatic tire of the present invention includes members constituting a general pneumatic tire such as a breaker, a case, an inner liner, and a bead apex, in addition to the tread, sidewall, wing, clinches, and DLC thin film. The rubber composition constituting each member is not particularly limited as long as it is generally used as a rubber composition for each member of a tire.

  The pneumatic tire of the present invention can be manufactured by forming a DLC thin film on the outer surface of a sidewall of a pneumatic tire obtained by a normal method. That is, the plasma CVD method is applied to the outer surface of a sidewall of a pneumatic tire obtained by vulcanizing an unvulcanized tire obtained by bonding each member such as a tread and a sidewall on a tire molding machine in a vulcanizer. Thus, the pneumatic tire of the present invention can be obtained by forming the DLC thin film.

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

Examples 1 and 2 and Comparative Examples 1 to 3
Each test tire (size: 155 / 65R14) was prepared, and a DLC thin film having the conditions (film thickness and formation position) shown in Table 1 was subjected to an ECR-plasma CVD method (a DLC composite film forming apparatus (DLC manufactured by Shimadzu Corporation)). -MR3), raw material gas: ethane). The film thickness of the DLC thin film was measured by the X-ray reflectivity method (using XRD-7000 manufactured by Shimadzu Corporation).

Details of the rubber composition for tread and the rubber composition for sidewall used in the test tires of all Examples and Comparative Examples are shown below.
Rubber composition for tread Carbon black content: 20 parts by mass with respect to 100 parts by mass of rubber component Volume resistivity: 1.0 × 10 ⁹ Ω · cm
tan δ: 0.25
Rubber composition for side wall Carbon black content: 20 parts by mass with respect to 100 parts by mass of rubber component Volume resistivity: 1.0 × 10 ⁹ Ω · cm
tan δ: 0.25
About other site | parts, each member comprised with the rubber composition of the general mixing | blending was unified and used. In addition, the test tire of Comparative Example 2 has an insulation with a high electrical conductivity composed of a rubber composition for insulation having a volume resistivity of 1.0 × 10 ⁴ Ω · cm between the case and the sidewall. Arranged between them.

  The following evaluation was performed using the obtained test tire.

<Electric resistance value 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. Note that the electrical resistance value of the tire is 1.0 × 10 ⁸ Ω or less as a performance target value. The evaluation results are shown in Table 1.

<Rolling resistance characteristics>
The rolling resistance is measured in accordance with ISO 28580 (JIS D 4234), and the result is shown as an index with Comparative Example 1 as 100. A smaller index indicates a lower rolling resistance and better rolling resistance characteristics. The evaluation results are shown in Table 1.
(Rolling resistance characteristic index) =
(Rolling resistance of each test tire) / (Rolling resistance of Comparative Example 1) × 100

<Appearance after running>
Each test tire was mounted on a passenger car having a displacement of 650 cc, and the appearance (DLC thin film) after traveling 10,000 km on the asphalt road surface (dry) was visually observed and evaluated according to the following criteria. The evaluation results are shown in Table 1.
○: The state of the DLC thin film was not changed from that before running, and no peeling occurred.
X: DLC thin film peeling or discoloration is observed.

  From the results in Table 1, by forming a diamond-like carbon thin film having a thickness of 1 to 10 μm on the outer surface of the sidewall in the pneumatic tire in which the tread and the sidewall are composed of a rubber composition having a high volume resistivity. It can be seen that a pneumatic tire excellent in electrical conductivity and rolling resistance characteristics can be obtained in spite of having no insulation with high conductivity.

10 DLC thin film 21 Side wall 22 Wing 23 Clinch 24 Rim S Shoulder part B Bead part

Claims (2)

A tread composed of a rubber composition for a tread having a volume resistivity of 1.0 × 10 ^{9 to} 1.0 × 10 ¹³ Ω · cm, and
Having a sidewall composed of a rubber composition for sidewall having a volume resistivity of 1.0 × 10 ^{9 to} 1.0 × 10 ¹³ Ω · cm;
It is a pneumatic tire having no insulation composed of a rubber composition for insulation having a volume resistivity of 1.0 × 10 ⁸ Ω · cm or less,
A pneumatic tire having a diamond-like carbon thin film with a film thickness of 1 to 10 μm formed on a sidewall outer surface by a plasma CVD method. The diamond-like carbon thin film is
The pneumatic tire according to claim 1, wherein the pneumatic tire is formed continuously from a shoulder portion to a bead portion of the pneumatic tire.

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