JP2000225618A - Manufacturing method for pneumatic tires - Google Patents

Abstract

(57) [Summary] (Corrected) [PROBLEMS] To provide a tire manufacturing method in which a conductor is provided on a defective conductive tread rubber in which a tread rubber is formed with a rubber composition containing carbon black without impairing tire performance. A belt (4) is provided outside a crown portion of a carcass (3).
And the outside thereof is covered with a tread rubber 5 made of a poorly conductive rubber composition, and a sidewall rubber 6 of a good conductive rubber composition having a Mooney viscosity of at least 10 lower than that of the tread rubber is applied to a carcass 3 or a belt on a side portion. A ground end line parallel to the tire cross-section center line CL passing through the end A of the ground width W when a specified load is applied at a specified internal pressure when the green tire 1 arranged so as to be sandwiched and terminated by the tread rubber 4 and the tread rubber 5 is applied. 7 and radially outer end E of sidewall rubber 6
The diameter d is 1 to 15 at a position corresponding to a portion sandwiched by sidewall end lines 8 parallel to the center line CL of the tire cross section passing through.
Vulcanization molding is performed using a mold 2 provided with a rubber induction hole h of mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a pneumatic tire which is not charged even though a tread is formed with a rubber composition having poor conductivity.

[0002]

2. Description of the Related Art In order to meet the social demands for reducing carbon dioxide emissions, the fuel efficiency of automobiles has been improved, and tires are required to have reduced rolling resistance. Generally, if the rolling resistance is reduced, the skid resistance on wet road surfaces tends to deteriorate. If carbon black, which is widely used as a reinforcing agent for a tread rubber composition, is changed to silica, rolling resistance can be reduced without impairing skid resistance on a wet road surface, and the above-mentioned problems are solved. However, since silica has poor electrical conductivity, a rubber composition using this as a main reinforcing agent has poor conductivity, and when used in a tread of a tire, the tire rubs against a road surface during use of the tire to generate static electricity. Has the drawback of causing static electricity troubles. For example, when a worker who does not wear electrified shoes at a gas station opens the lid of the car's gasoline tank, it is grounded via the worker and discharges sparks. Noise may occur in other radio equipment. In the case of the former, there is a risk that the gasoline may catch fire and cause a fire.

[0003] In order to solve the above-mentioned problems of a tire having a tread formed of a defective conductive rubber composition, a conductor made of a good conductive rubber composition is penetrated through tread rubber to form a belt in the circumferential direction of the tire or to be spaced apart from the tire. A method of burying in a shape and grounding static electricity via a conductor has been proposed. The tire in which the conductor is embedded by penetrating the tread rubber, simultaneously extrudes the bad conductive rubber composition and the good conductive rubber composition and simultaneously extrudes the good conductive rubber composition extruded body with the thickness of the bad conductive rubber composition extruded body. It is manufactured using a tread rubber extruded product formed by an extruder provided with a special die having a structure capable of being penetrated and embedded in the vertical direction (Japanese Patent Application Laid-Open Nos. 8-34204 and 9-204). 7111
2).

[0004]

A tire provided with a conductor by the above method requires an extra rubber composition for forming the conductor, which increases the cost. Also, tires in which conductors are buried in a belt circumferential direction do not place importance on tire performance alone in parallel in the tread, in other words, tire performance is sacrificed because a rubber composition sacrificing tire performance is arranged. However, tires that are buried in a point shape with the conductors separated from each other require a special ferrule, are complicated in work, lower in productivity, and have a drawback of increasing manufacturing costs.

[0005] The present invention provides a method for forming a conductive material on a poorly conductive tread rubber without changing the production equipment used in the production of a conventional tire in which a tread rubber is formed from a rubber composition containing carbon black without impairing tire performance. The purpose of the present invention is to provide a tire manufacturing method.

[0006]

According to the present invention, a belt is arranged outside a crown portion of a carcass, the outside of the belt is covered with a tread rubber made of a poorly conductive rubber composition, and a belt is formed from a radially inner end of a side portion. So-called TOS, which extends in the direction of the belt and is covered with a carcass or belt and tread rubber in the vicinity of the end of the belt and covers the side portion with a sidewall rubber that terminates
(TREAD OVER SIDE WALL) A sidewall rubber of a green tire having a structure is formed of a highly conductive rubber composition having a Mooney viscosity at least 10 lower than that of a tread rubber, and the tire is filled with a specified internal pressure and a specified load is applied. Through the end of the contact width when passing through the contact edge line parallel to the tire section center line and the sidewall end line parallel to the tire section center line through the radial outer end of the sidewall rubber A method for producing a pneumatic tire, comprising vulcanizing and molding the green tire using a mold provided with a rubber induction hole having a diameter d of 1 to 15 mm at a corresponding position.

[0007]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a state in which a green tire is vulcanized and molded by a mold used in the present invention, and FIG. 2 is a partially enlarged view of a tread shoulder portion in FIG. Reference numeral 1 denotes a green tire, and reference numeral 2 denotes a mold.
In the green tire 1, a belt 4 is disposed outside a crown portion of a carcass 3, the outside thereof is covered with a tread rubber 5 made of a defective conductive rubber composition, and a side portion extends outward from an inner end in a tire radial direction. Near the center of the tire from the end of the belt 4 or near the opposite side, the carcass 3
Alternatively, it has a so-called TOS structure in which it is sandwiched between the belt 4 and the tread rubber 5 and covered with a sidewall rubber 6 that terminates. The sidewall rubber 6 is formed of a rubber composition containing carbon black, having good conductivity, and having a Mooney viscosity at least 10 lower than that of the tread rubber. During the vulcanization molding, the thickness t of the tread rubber at the portion that contacts the opening of the induction hole h of the mold described below is preferably set to 1 to 5 mm.

In the present application, the electric resistance value is 10 ⁷ Ω · cm.
The following rubber composition is called a good conductive rubber composition, and the larger one is called a poor conductive rubber composition. The good conductive rubber composition can be obtained by blending natural rubber, gen-based synthetic rubber alone or in combination with a rubber component having low electric resistance such as carbon black, carbon fiber, graphite and metal powder. Tread rubber composition used in the present invention,
The rubber component is obtained by mixing silica as a reinforcing agent, or a further small amount of carbon black is added as a coloring agent.

The mold 2 for vulcanizing and molding the green tire 1 passes through the end A of the contact width W when the vulcanized tire is filled with a prescribed internal pressure and a prescribed load is applied, and the tire cross-section center line CL From the inner surface to the outer surface at a mold position corresponding to a portion sandwiched between the sidewall end line 8 parallel to the tire cross-section center line CL through the ground end line 7 parallel to the tire and the radially outer end E of the sidewall rubber 6. Is provided with a rubber inducing hole h having a diameter d of 1 to 15 mm. A counterbore 9 is provided at the opening of the rubber attraction hole h on the inner side of the mold as required.

The green tire 1 is placed in the mold 2, the outer surface of the mold is heated to a temperature of 150 to 200 ° C., and a pressure of 0.5 to 1.5 MPa is applied to the inside of the bladder 10 which is inserted into and adheres to the inner surface of the green tire 1. Temperature 150-250 ° C
Hot water or nitrogen gas is introduced, and the green tire 1 is pressurized and heated to perform vulcanization molding. At this time, the tread rubber and the sidewall rubber softened by the high temperature enter the rubber attraction hole h as shown in FIG. 2, and the tread rubber moves to the rubber attraction hole, and a low viscosity side wall is formed at the blank portion. The rubber flows in preferentially, and the sidewall rubber composition penetrates the tread rubber and extends into the rubber inducing hole. The conductive portion 12 is formed by cutting the protruding portion 11 formed into the rubber attraction hole h along the cut line CC 'after vulcanization molding.

If the difference between the Mooney viscosities of the tread rubber and the sidewall rubber is smaller than 10, the tread rubber moves to the rubber inducing hole and the sidewall rubber cannot flow preferentially into the blank portion, so that the necessary conductivity is required. Is not formed. If the thickness of the portion in contact with the opening of the tread rubber attraction hole is less than 1 mm, the tread rubber wears out and the sidewall rubber that does not have sufficient wear resistance is exposed, and if it exceeds 5 mm, the sidewall rubber is completely removed. Since it does not extend to the tread rubber surface, a required level of conductivity cannot be obtained. If the diameter of the through hole is less than 1 mm, the penetration of the rubber becomes insufficient and no conductive portion is formed. If the diameter is more than 15 mm, the exposed area of the sidewall rubber becomes large and the portion is unevenly worn.

[0012]

EXAMPLES 100 parts by weight of the rubber component shown in Table 1 (hereinafter, part by weight is simply referred to as "part") are blended with the compounding agent shown in Table 1 in the ratio (part) shown in Table 1, and according to a standard method. The mixture was mixed to obtain a mixed rubber. The Mooney viscosity of the mixed rubber was measured and the results are shown in Table 1. Further, a part of the mixed rubber was vulcanized, and the electric resistance was measured according to JIS K6911. The results are shown in Table 1.

[0013]

[Table 1]

Using the above-mentioned mixed rubber, the tire size 185 / 65R having the structure shown in FIG.
Fourteen green tires were prototyped. The tread rubber thickness in the table indicates the thickness t at a position where the tread rubber comes into contact with the attraction hole provided in the mold when vulcanization molding is performed. The prototype green tire was provided with four rubber attraction holes having diameters shown in Table 2 at positions substantially corresponding to the portion between the grounding end line 7 and the sidewall end line 8 of both tire shoulders at substantially equal intervals on the circumference. Vulcanization molding was performed using a mold according to a standard method. The obtained prototype tire is filled with a specified internal pressure and placed on an iron plate, one of the conductive portions is positioned so as to be in contact with the iron plate, a specified load is applied, and an electrode is brought into close contact with each of the sidewall and the iron plate to reduce electric resistance. Measurements were made to confirm the presence or absence of conductivity. Then, after the prototype tire was mounted on a passenger car and traveled about 20,000 km, a visual inspection of the occurrence of uneven wear was performed. The results are shown in Table 2. The difference in Mooney viscosity in the table indicates the difference in Mooney viscosity between the tread rubber composition and the sidewall rubber composition.

[0015]

[Table 2]

[0016] The prototype 2 tire using a mold having a diameter of the rubber induction hole of 0.2 mm has poor conductivity because the diameter of the rubber induction hole is too small to form an effective conductive portion. The third prototype tire using a mold having a rubber attraction hole diameter of 20.0 mm has good conductivity, but uneven wear occurred due to an excessively large conductive portion. The prototype 4 tire having a tread rubber thickness of more than 5 mm at a position where the tread rubber is in contact with the attraction hole has an excessively large tread rubber thickness, so that the sidewall rubber cannot completely penetrate the tread rubber, resulting in poor conductivity. Since the difference in Mooney viscosity between the tread rubber composition and the sidewall rubber composition is smaller than 10 in the prototype 5 tire, the sidewall rubber does not preferentially flow into the blank after the tread rubber has flowed into the rubber inducing hole, Poor conductivity due to incomplete formation of conductive parts.

[0017]

As described above, the green tire is sandwiched between the tread rubber and the carcass or belt at the radially outer end by using a well-conductive sidewall rubber having a Mooney viscosity at least 10 smaller than that of the tread rubber. To a structure that terminates in the vicinity of the belt end, and vulcanization-molding is performed by using a mold having a rubber attraction hole at a position corresponding to the portion between the grounding end line 7 and the sidewall end line 8 of the green tire. A conductive portion is formed. As a result, even if the tread rubber has poor conductivity, the static electricity generated in the tire is grounded through the conductive portion formed by the attraction hole, and the trouble caused by the static electricity is eliminated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a green tire is vulcanized by a mold used in the present invention.

FIG. 2 is a partially enlarged view of a tread shoulder portion of FIG.

[Explanation of symbols]

Reference Signs List 1 Green tire 2 Mold 3 Carcass 4 Belt 5 Tread rubber 6 Side wall rubber 7 Ground end line 8 Side wall end line 9 Counterbore A Ground width end when specified load is applied at specified internal pressure CL Tire cross-section center line d Diameter of rubber attraction hole E Radial outer end of sidewall rubber h Rubber attraction hole t Thickness of tread rubber at position where it contacts rubber attraction hole W Ground contact width at specified internal pressure and specified load

Claims (3)

[Claims] 1. A belt (4) is arranged outside a crown portion of a carcass (3), the outside of which is covered with a tread rubber (5) made of a poorly conductive rubber composition, and a Mooney viscosity tread rubber is provided on an outer surface of a side portion. A sidewall rubber (6) of at least 10 lower good conductive rubber composition extends outwardly from the radially inner end of the tire to the carcass (3) or belt (4) and the tread rubber ( 5)
A green tire (1) arranged so as to be sandwiched and terminated at the end of the tire, a tire cross-sectional center line (CL) passing through the end (A) of the contact width (W) when the tire is subjected to a specified load at a specified internal pressure. ) And a portion sandwiched between sidewall end lines (8) parallel to the tire section center line (CL) passing through the radially outer end (E) of the sidewall rubber (6). Vulcanization molding using a mold (2) provided with a rubber attraction hole (h) having a diameter d of 1 to 15 mm at a position corresponding to the above. 2. The method for producing a pneumatic tire according to claim 1, wherein a green tire having a thickness (t) of 1 to 5 mm of the tread rubber at a position in contact with the rubber attraction hole h is vulcanized. 3. The mold according to claim 1, wherein a counterbore is provided at an opening of the rubber attraction hole on the inner surface side of the mold.
The method for producing a tire according to any one of the above.