JP3514539B2 - Pneumatic tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for automobiles which has a reduced rolling resistance without reducing the conductivity of the tire.

[0002]

2. Description of the Related Art In recent years,
The demand for low fuel consumption for automobiles is increasing. Here, since the performance of the tire, particularly the rolling resistance of the rubber material forming the tread has a great influence on the fuel consumption, the development of a rubber composition for a tread having a small rolling resistance is under way. In order to reduce the rolling resistance of the rubber composition, the amount of carbon black as a reinforcing agent is reduced, or while using a low grade carbon black, precipitated silica or anhydrous silica in order to prevent deterioration of the reinforcing property, firing Attempts have been made to blend non-carbon black type reinforcing agents such as clay and hard clay.

However, since carbon black not only acts as a reinforcing agent but also serves to reduce the electric resistance of the tread rubber, reducing the amount of carbon black compounded and the grade of the tread, and hence the conductivity of the tire. It caused a new problem of decreased sex.
Here, the static electricity accumulated in the vehicle body reaches the tread portion from the tire rim, through the bead portion and the sidewall portion.
Therefore, if the tread rubber material has poor conductivity, static electricity cannot flow to the ground, and static electricity is accumulated. When a tire having low conductivity is mounted on a vehicle, static electricity accumulated in the vehicle body may cause a discharge phenomenon when the tire passes over a manhole or the like, or may cause an obstacle to electronic equipment of the vehicle. In addition, a discharge phenomenon may occur when refueling a low boiling hydrocarbon fuel such as gasoline, which is dangerous.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire having improved conductivity.

[0005]

That is, as shown in FIG. 1, a pneumatic tire according to the present invention is wound around from a tread portion 1 to a sidewall portion 2 to a bead core 6 from inside to outside. It has a carcass layer 7 to be stopped. The carcass layer 7 is composed of a plurality of cords arranged in parallel to the tire radial direction. The belt layer 8 is placed radially outward of the carcass layer 7. The belt layer 8 is 2
It consists of a ply in which the above high elasticity cords are arranged in parallel.
FIG. 1 shows an example of two plies, and the cords of each ply are arranged so as to intersect with each other.

A conductive thin film 3 is laid on the surfaces of the tread portion 1 and the sidewall portion 2. The conductive thin film 3 also covers the surface of the groove 4 of the tread portion 1. Also,
Although FIG. 1 shows only the right half, the left half has a similar structure. The rubber composition constituting the tread portion 1 (rubber composition for tread) contains 50 parts by weight or less of carbon black with respect to 100 parts by weight of the rubber component and 25% by weight or less of the entire rubber composition. is there. In addition, a non-carbon black type reinforcing agent is blended in place of the reduced amount of carbon black. Here, the non-carbon black type reinforcing agent means silicas such as precipitated silica and silicic acid anhydride, clays such as calcined clay and hard clay, calcium carbonate and the like. Of these, silicas are particularly preferably used. The blending amount of the non-carbon black type reinforcing agent is appropriately selected according to the required strength depending on the blending amount of carbon black and the type of tire. The type of the rubber component in the rubber composition for tread is not particularly limited, and natural rubber; diene synthetic rubber such as butadiene rubber and SBR; or a combination thereof can be appropriately used. Further, it is preferable to add a silane coupling agent such as bis (triethoxysilylpropyl) -tetrasulfide or γ-mercaptopropyltrimethoxysilane.

The rubber composition (rubber composition for sidewalls) constituting the sidewall portion 2 contains carbon black in an amount of 40 parts by weight or less with respect to 100 parts by weight of the rubber component and 25 parts by weight of the entire rubber composition. It is less than or equal to weight%.
The type of rubber component in the rubber composition for sidewalls is not particularly limited, and natural rubber; butadiene rubber, S
A diene-based synthetic rubber such as BR; or a combination thereof can be appropriately used.

In the rubber composition (rubber composition for conductive thin film) constituting the conductive thin film 3, the carbon black content is 60 parts by weight or more per 100 parts by weight of the rubber component and the total amount of the rubber composition. It is 35% by weight or more. The type of the rubber component in the rubber composition for a conductive thin film is not particularly limited, and natural rubber; diene-based synthetic rubber such as butadiene rubber and SBR; or a combination thereof can be used as appropriate. In order to improve ozone resistance, it is preferable to use 25 to 50% by weight of the rubber component as EPDM.

The tire having the tread portion 1 and the sidewall portion 2 made of the rubber composition having the above composition has a small amount of carbon black, and
It has low rolling resistance and can meet the demand for low fuel consumption. On the other hand, the decrease in the reinforcing property due to the decrease in the amount of carbon black is prevented by blending a non-carbon black type reinforcing agent such as silica. The decrease in the conductivity of the tread portion 1 and the sidewall portion 2 due to the incorporation of the non-carbon black-based reinforcing agent, which is inferior in conductivity to the carbon black, is caused by the conductive thin film 3 having excellent conductivity. It is prevented by being laid on the surface of the sidewall portion 2. That is, the conductive thin film 3c laid on the surface of the sidewall portion 2 from the tire rim 5, the tread portion 1
This is because the static electricity accumulated in the vehicle body can flow to the ground through the conductive thin films 3a and 3b laid on the surface.

The thickness of the conductive thin film is preferably 0.2 mm or less, more preferably 0.1 mm or less. Since the rubber composition for a conductive thin film contains a large amount of carbon black having excellent conductivity as described above, it has a higher rolling resistance than a general tread rubber. Therefore, if the thickness of the conductive thin film exceeds 0.2 mm, the rolling resistance increases. Since the conductive thin film 3b laid on the tread groove 4 remains even after the conductive thin film 3a laid on the grounding surface of the tread portion 1 is worn, the conductive thin film 3b laid on the surface of the tire rim 5 and the sidewall portion 2 is left. Through the conductive thin film 3c and the conductive thin film 3b laid on the tread groove 4
Can discharge static electricity to the ground.

The method of laying the conductive thin film on the tread portion 1 and the sidewall portion 2 is not particularly limited. For example,
It can be provided by vulcanization molding while covering an unvulcanized rubber sheet made of the rubber composition for a thin film on the surfaces of the tread portion and the sidewall portion of the green tire. However, with such a method, it is difficult to form an unvulcanized rubber sheet having a thickness of less than 0.1 mm, and thus a conductive thin film having a thickness of less than 0.1 mm cannot be formed. The conductive thin film having a thickness of less than 0.1 mm is subjected to vulcanization molding after spraying or applying a thin film rubber composition solution obtained by dissolving the conductive thin film rubber composition in an organic solvent onto the tread surface of a raw tire. Therefore, it can be easily obtained.

The tread pattern of the pneumatic tire to which the present invention is applied is not particularly limited, but as shown in FIG.
It is preferable to have not only the vertical groove 11 but also the horizontal groove 12 whose end reaches the sidewall portion 2. Here, the lateral groove 12
Is not limited to one that is orthogonal to the vertical groove 11, and may be a groove that intersects with the vertical groove 11. FIG. 2 shows an example in which a vertical groove 11 is provided with a lateral groove 12 that intersects diagonally. By providing the lateral groove 12 extending from the ground contact surface to the sidewall portion 2, even if the conductive thin film is worn, the thin film provided in the tread groove 4 portion is grounded while running, and the sidewall portion 2 is provided. This is because the static electricity from can be released to the ground.

The difference between the groove depth of the lateral groove 12 and the groove depth of the vertical groove 11 is preferably 0 to 1.6 mm . When the wear of the tread rubber itself continues following the conductive thin film laid on the tread portion 1, the lateral groove 12 may disappear, so at the time of tire replacement (when the groove depth of the vertical groove 11 is worn to 1.6 mm). This is because it is desirable to secure a groove depth such that the lateral groove 12 remains.

[0014]

EXAMPLES The present invention will be described below based on specific examples. [Preparation of Rubber Composition for Tread] Three kinds of rubber compositions for tread (A, B, having the composition (parts by weight) shown in Table 1
C) was compounded. In Table 1, NS-116 (trade name) manufactured by Nippon Zeon was used as s-SBR. This is a non-oil extended rubber having a styrene content of 20% by weight and a vinyl content of 63%. As the carbon black, N351 (trade name) manufactured by Showa Cabot Corporation was used. As silica,
Ultrasil VN3 manufactured by Degussa was used, and Si-69 manufactured by Degussa was used as the silane coupling agent.

Further, regarding various rubber compositions, tan δ
Was measured and the results are also shown in Table 1. Tan δ
Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho,
It was measured under the conditions of initial elongation of 10%, dynamic strain of 2%, and measurement temperature of 70 ° C.

[0016]

[Table 1]

[Rubber Composition for Sidewalls] Two types of rubber compositions for sidewalls (a, b) having the compositions (parts by weight) shown in Table 2 were blended. In Table 2, as the butadiene rubber, BR150L manufactured by Ube Industries, Ltd. was used. This is butadiene having a high cis content of 98% of cis-butadiene. As carbon black (FEF),
Showa Cabot N550 was used.

Further, regarding various rubber compositions, tan δ
Was measured and the results are also shown in Table 2.

[0019]

[Table 2]

[Preparation of Rubber Composition for Thin Film] A rubber composition for a thin film having a compounding composition (parts by weight) shown in Table 3 was prepared. As EPDM, ESPRENE manufactured by Sumitomo Chemical Co., Ltd.
586 was used. It has a propylene ratio of 20% by weight and an iodine value of 36 ENB. BR150L manufactured by Ube Industries was used as the butadiene rubber.

Further, regarding various rubber compositions, tan δ
Was measured and the results are also shown in Table 3.

[0022]

[Table 3]

[Effect of Thin Film] A tire (195 / 65R15 PERFORMA 8000 TL) was prepared by combining the tread rubber shown in Table 1 and the sidewall rubber shown in Table 2. This tire is provided with a lateral groove extending from the tread portion to the sidewall portion. On the tire thus prepared, a thin film composed of the rubber composition for a thin film shown in Table 3 (0.2 to
0.1 mm) was laid in the tread portion and the sidewall portion and a tire in which a thin film was not laid were prepared, and the electric conductivity, rolling resistance and ozone resistance of the tire were measured based on the following evaluation methods. evaluated. The evaluation results are shown in Table 4. [Evaluation Method] The rolling resistance was measured with an indoor bench tester under the conditions of an internal pressure of 2.0 kg / cm ₂ and a load of 400 kgf.

The electric conductivity tire was attached to an aluminum wheel of 15 × 6.0 JJ, and the internal pressure was set to 2.0 ksc. This tire was pressed against a copper plate with a load of 400 kg, a voltage of 1000 V was applied between the copper plate and the wheel center, and the conductivity was measured with a Megohmmeter. If the electric conductivity is 1.0 MΩ, the problem due to poor conductivity does not occur.

Ozone resistance 15 × 6.0J with a tire adjusted to an internal pressure of 2.0 ksc
When mounted on J's aluminum wheel, ozone concentration is 50
It was installed in a chamber having a pphm and an ambient temperature of 40 ° C. Under such conditions, the presence or absence of cracks on the sidewall surface after being left for about 2 weeks was visually observed.

[0026]

[Table 4]

As can be seen from Table 4, by laying a conductive thin film containing EPDM, the electric conductivity of the tire is lowered and the ozone resistance is also improved (see Tire Nos. 7 to 12). On the other hand, unless the compounding amount of carbon black in the tread and sidewall rubber composition is less than or equal to a predetermined amount, rolling resistance is not reduced (tires Nos. 7 and 11 and tires Nos. 8 to 10 and 12).
reference).

Therefore, a pneumatic tire having a tread and a sidewall made of a rubber composition containing carbon black in a predetermined amount or less and having a conductive thin film is
Low rolling resistance and excellent conductivity. [Effects of Providing Lateral Grooves] Next, effects of providing the lateral grooves in the tread portion will be described.

Tire No. 7, 12 (see Tables 1 to 3 for rubber composition), and tire No. Electric conductivity of a tire (tire No. 13) equivalent to that of No. 7 except that there was no lateral groove was measured immediately after tire production (initial stage) and after the tire was worn until the thin film on the ground contact surface disappeared (after abrasion). Rolling resistance and ozone resistance were evaluated based on the above evaluation methods. The results are shown in Table 5. The ozone resistance after abrasion was not measured.

[0030]

[Table 5]

As can be seen from Table 5, in the tires having lateral grooves (Nos. 7 and 12), the electric conductivity after abrasion is slightly lower than the initial value, but the conductivity is not a problem. In the tire having no lateral groove (No. 13), the electric conductivity is reduced to the same degree as that of the tire having no conductive thin film, and the conductivity problem occurs. On the other hand, with regard to rolling resistance, regardless of the presence or absence of the lateral groove, after rolling, both are slightly smaller than the initial values. Therefore, in a pneumatic tire in which the tread and the sidewall are made of a predetermined rubber composition, a conductive thin film is laid on the tread portion and the sidewall portion, and a lateral groove is provided, a tire from a new state to a time of replacement is required. Through, the rolling resistance is reduced without causing a conductivity problem.

[0032]

INDUSTRIAL APPLICABILITY The pneumatic tire of the present invention does not cause a problem of conductivity although the tread portion and the sidewall portion are made of a rubber composition containing less carbon black to improve rolling resistance. . Further, a pneumatic tire using a conductive thin film containing EPDM has excellent ozone resistance and weather resistance, and does not cause a problem of deterioration of the appearance of the sidewall. Further, in the tire having the lateral groove provided from the tread portion to the sidewall portion, the rolling resistance can be reduced throughout the period from the new state to the time of replacement without causing a problem of conductivity. That is, it is possible to meet the demand for fuel economy.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a pneumatic tire according to the present invention on the right side of the equatorial plane.

FIG. 2 is a partial cross-sectional perspective view of a pneumatic tire having lateral grooves.

[Explanation of symbols]

1 tread section 2 Side wall part 3 Conductive thin film 11 flutes 12 lateral grooves

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-5-271477 (JP, A) JP-A 7-48476 (JP, A) JP-A 61-122003 (JP, A) JP-A 57- 34140 (JP, A) JP 61-31462 (JP, A) JP 6-305308 (JP, A) JP 7-40712 (JP, A) JP 4-362404 (JP, A) JP-A-63-301244 (JP, A) JP-A-62-148543 (JP, A) Actual development Sho-63-176805 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60C 1/00-19/12

Claims (4)

(57) [Claims] 1. The rubber composition constituting the tread portion (1) contains carbon black in an amount of 50 parts by weight or less based on 100 parts by weight of the rubber component and 25% by weight or less of the entire rubber composition. The rubber composition containing the non-carbon black type reinforcing agent and constituting the sidewall part (2) has a compounding amount of carbon black of 40 parts by weight or less with respect to 100 parts by weight of the rubber component and 25% by weight of the entire rubber composition. A pneumatic tire having a weight% of less than or equal to the tread portion (1) and the sidewall portion (2) having a conductive thin film (3) laid thereon, and a rubber composition constituting the conductive thin film (3). Is 6 when the amount of carbon black is 100 parts by weight of the rubber component.
It is 0 parts by weight or more and 35% by weight or more of the entire rubber composition, and intersects with the vertical groove (11) provided along the circumferential direction of the tire.
Difference between the groove depth of the vertical groove and the groove depth of the vertical groove
A transverse groove (12) having a groove depth of 0 to 1.6 mm
The end of the lateral groove (12) reaches the sidewall part (2).
Pneumatic tire characterized by being provided in the way . 2. A rubber set constituting the conductive thin film (3)
25-50% by weight of the rubber component in the product is EPDM
The pneumatic tire according to claim 1, wherein: 3. The conductive thin film (3) has a thickness of 0.2 m.
It is less than or equal to m, The said of Claim 1 or 2 characterized by the above-mentioned.
Pneumatic tires. 4. The non-carbon black reinforcing agent is a
It is Rica, It is any one of Claims 1-3 characterized by the above-mentioned.
Pneumatic tire described in 3.