JP2013096040A - Rubber/cord composite material and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost rubber/cord composite material and a pneumatic tire which can attempt high mileage of a vehicle by reducing weight.SOLUTION: Provided is a rubber/cord composite material formed by coating with rubber compositions a cord which is made of a steel round pipe 1 whose outer diameter d is 10-15 mm and wall thickness t is 1-3.5 mm by connecting to be ring-shaped. The rubber/cord composite material is for use in a bead. A pneumatic tire for which the rubber/cord composite material is used is also provided.

Description

  The present invention relates to a rubber-cord composite that is reduced in weight and cost, and a pneumatic tire using the rubber-cord composite.

  In the production of pneumatic tires (hereinafter also simply referred to as “tires”), various rubber-cord composites have been conventionally used. For example, on the bead part that is to be attached to the wheel rim, several small steel cords (bead wires) are layered for the purpose of securely fitting with the wheel rim and maintaining the internal air pressure. In addition, a bead core formed by winding a rubber composition on a bead core is used (for example, Patent Documents 1 and 2).

JP 2003-205713 A JP 2003-312214 A

  However, since the rubber-cord composite in which the cord is wound in such a manner is heavy, the weight of the pneumatic tire in which such a rubber-cord composite is used must be increased. A vehicle with heavy tires causes a reduction in fuel efficiency.

  In addition, in a pneumatic tire using such a rubber-cord composite, the adhesion between the rubber and the cord is lowered due to long-term use, and the cord may be peeled off from the rubber. Since the cord peeled from the rubber tries to return to the original straight state, it jumps out to the tire surface and damages the tire. For this reason, it has been conventionally performed to apply a coumarone resin or the like to the cord surface to suppress a decrease in adhesion between the rubber and the cord. However, such processing causes an increase in cost.

  In view of the above-described problems of the prior art, the present invention can provide a low-cost rubber / cord composite and a pneumatic tire while reducing the weight of the vehicle and reducing the fuel consumption of the vehicle. Is an issue.

The invention described in claim 1
A rubber cord is formed by coating a rubber composition on one cord formed by connecting steel round pipes having an outer diameter of 10 to 15 mm and a wall thickness of 1 to 3.5 mm in an annular shape. Code complex.

The invention described in claim 2
The rubber-cord composite according to claim 1, wherein the rubber-cord composite is used for a bead.

The invention according to claim 3
A pneumatic tire comprising the rubber-cord composite according to claim 2.

  According to the present invention, since the rubber / cord composite can be reduced in weight, it is possible to reduce the fuel consumption of the vehicle, and further provide a rubber / cord composite and a pneumatic tire that are reduced in cost. can do.

It is a perspective view of the edge part of the round pipe used for preparation of the rubber cord composite concerning one embodiment of the present invention. It is a top view of the code | cord | chord used for preparation of the rubber cord composite_body | complex which concerns on one embodiment of this invention.

  Hereinafter, the present invention will be specifically described based on embodiments.

1. Code First, the code will be explained.

  In the present embodiment, as a cord of the rubber-cord composite, a cord in which both ends of a steel round pipe excellent in strength are joined by welding or the like and joined in an annular shape is used.

  FIG. 1 shows a perspective view of the end of such a round pipe, and FIG. 2 shows a plan view of a cord formed in an annular shape. In FIG. 1, d is the outer diameter of the round pipe 1, and t is the wall thickness. In FIG. 2, D is the inner diameter of the cord 2.

  The material of the steel of the round pipe 1 is not particularly limited, but if the thickness is too thin, it cannot maintain the same strength (breaking strength) as before. Considering main characteristics such as strength and weight, it is preferable to use a steel round pipe having an outer diameter d of 10 to 15 mm and a wall thickness t of 1 to 3.5 mm, as shown in the examples described later. The inner diameter D of the cord 2 is appropriately set according to the tire size and the like.

  In this way, by forming an annular cord using a steel round pipe, it is lighter while having the same strength as a conventional cord wound with multiple thin steel cords. Can get the code.

2. Rubber / Cord Composite The rubber / cord composite of the present embodiment is manufactured by coating the outer peripheral surface of the cord 2 with a rubber composition using one cord 2 described above.

  In such a rubber-cord composite, since the cord 2 is lightened, the rubber-cord composite is also lightened and the tire is also lightened. Further, by reducing the weight of the tire, the fuel consumption of the vehicle can be reduced.

  And the rubber-cord composite produced using an annular cord formed by joining round pipes, the cord-rubber peels off due to a decrease in the adhesion between the cord and rubber over a long period of use. However, since there is no risk of the cord jumping out on the tire surface, the conventional treatment using coumarone resin or the like becomes unnecessary. As a result, cost can be reduced.

1. Production of Bead (1) Production of Bead Wire (Bead Core) Using a steel round pipe having an outer diameter and a wall thickness shown in Table 1, a cord formed in an annular shape having an inner diameter of 1203.5 mm was produced. 4 and Comparative Example 2-5 bead wires (bead cores).

The composition of the steel round pipe is as follows.
C: 0.65-0.75 wt%
Mn: 0.30 to 0.60 wt%
S: 0.03 wt% or less
P: 0.03 wt% or less
Si: 0.15-0.35 wt%

  On the other hand, a steel cord having an outer diameter of 1.2 mm and the same composition as above was wound 19 times to produce a conventional type bead wire (bead core).

(2) Rubber coating Each bead wire was coated with a rubber composition having the following composition (thickness: 1 mm) to prepare a rubber-cord composite, which was used as each bead. The unit is phr.
NR: 65
SBR: 35
Carbon: 140
Zinc oxide: 5
Stearic acid: 4
Antioxidant: 1.3
Resin: 25
Sulfur: 5
Vulcanization accelerator: 0.9

  When coating the rubber composition, the bead wires of Comparative Examples 1 and 2 were previously coated with a coumarone resin on the cord surface.

2. Production of Pneumatic Tire Five 195 / 65R15 PCR tires were produced using each of the produced beads.

3. Evaluation (1) Evaluation Items The tire weight, rolling resistance, and wire jump-out rate were determined for each PCR tire produced, and the strength (breaking strength) and cost (unit price per meter) were determined for each bead wire. Here, the reason why the rolling resistance is evaluated is that weight reduction of the tire contributes to the rolling resistance.

(2) Measurement and its evaluation method (a) Tire weight The tire weight was measured and evaluated by an index when the tire weight of Comparative Example 1 was taken as 100. The larger the index, the heavier the tire.

(B) Rolling resistance A rolling resistance tester was used to measure the rolling resistance when the tire was run at a rim of 15 × 6JJ, an internal pressure of 230 kPa, a load of 3.43 kN, and a speed of 80 km / h, and a comparative example. Evaluation was based on an index when the rolling resistance of 1 was 100. The smaller the index, the better the rolling resistance.

(C) Jumping out of wires PCR tires were treated for 150 hours under wet heat deterioration conditions at a temperature of 80 ° C and a humidity of 98%, and H / S (high-speed endurance test) was performed based on the ECE30 standard to measure the number of wires jumping out. The ratio (wire jumping rate) was obtained.

(D) Strength Tensile strength was measured when the bead wire was pulled with a tensile tester (2005 model manufactured by INTESCO) and was broken, and evaluation was performed using an index when the strength of Comparative Example 1 was set to 100. The greater the index, the greater the power.

(E) Cost The unit price per 1 m of the bead wire was determined, and the evaluation was performed using an index when the unit price of Comparative Example 1 was set to 100. The higher the index, the higher the cost.

(3) Evaluation results The evaluation results are also shown in Table 1.

  From Table 1, it can be seen that the pneumatic tires of Examples 1 to 4 are lighter in weight and superior in rolling resistance than the pneumatic tire of Comparative Example 1. Such a reduction in tire weight can be expected to reduce the fuel consumption of the vehicle. It can be seen that the wire pop-out rate is 0, and the wire jump-out is prevented. Moreover, it turns out that these bead wires have the same strength or more as before.

  Such a result was obtained because a rubber-cord composite was produced using a cord in which a steel round pipe having an appropriate outer diameter and wall thickness was formed in an annular shape. And in Example 1- Example 4, since coumarone resin application | coating is not performed, it turns out that it is low-cost.

  From Table 1, it can be seen that the steel round pipe used in the present invention is preferably a round pipe having an outer diameter of 10 to 15 mm and a wall thickness of 1 to 3.5 mm shown in the examples.

  That is, Comparative Example 2 having an outer diameter and a wall thickness smaller than the above range is lighter than Comparative Example 1 and has excellent rolling resistance and wire pop-out rate, but has low strength.

  Further, Comparative Example 3 having an outer diameter and a wall thickness larger than the above range and Comparative Example 4 having a wall thickness larger than the above range are stronger and heavier than the comparative example 1, but heavier. Rolling resistance is inferior.

  Further, Comparative Example 5 having an outer diameter larger than the above range and a small wall thickness is superior to Comparative Example 1 in terms of wire pop-out rate, but is heavier, inferior in rolling resistance and strength.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to said embodiment. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

1 Round pipe 2 Cord d Outer diameter D Inner diameter t Thickness

Claims (3)

  A rubber cord is formed by coating a rubber composition on one cord formed by connecting steel round pipes having an outer diameter of 10 to 15 mm and a wall thickness of 1 to 3.5 mm in an annular shape. Code complex.   The rubber-cord composite according to claim 1, which is used for a bead.   A pneumatic tire using the rubber-cord composite according to claim 2.

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