JP3061356B2 - Manufacturing method for pneumatic tires - Google Patents

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 capable of preventing fine wrinkles and cracks from occurring at the bottom of a tread groove formed in a tread portion.

[0002]

2. Description of the Related Art Pneumatic tires, particularly pneumatic radial tires for passenger cars, require high running performance not only on dry road surfaces but also on wet road surfaces. Therefore, a tread groove having a relatively wide width, for example, extending linearly and continuously in the tire circumferential direction is arranged on the tread surface.

However, such a tread groove has cracks (TG) such as fine wrinkles and cracks at the groove bottom.
C) easily occurs. These cracks are generally minute and do not immediately affect the tire running performance, but they are easily noticeable, and when the tread groove width is large, there is a problem that the appearance of the tire is significantly impaired. .

The inventors of the present invention have conducted intensive studies on such a problem. As a result, when a tread groove is formed by vulcanizing a raw tire cover with a vulcanizing mold, a groove bottom portion of the tread groove is locally formed. When the tire is new, the value of the complex elastic modulus is about twice as large as that of the inner portion of the tread surface when the tire is new, and such high elasticity reduces the occurrence of the crack. I got the knowledge that it was earlier.

Further, it has been found that the complex elastic modulus at the bottom of the groove increases with time, and the degree of the increase is larger than that of the other parts.

Further, when manufacturing an unvulcanized tread rubber body to be mounted on a raw tire cover, concave portions e, e corresponding to tread grooves of a completed tire are extruded in advance by a die plate D as shown in FIG. It is also conceivable to reduce the influence of the local compressive force on the groove bottom during vulcanization.

However, according to experiments by the present inventors, even when the above-described method is used, when rubber is extruded,
Although the tread rubber body is not vulcanized, a large compressive force acts on the bottom portion of the concave portion e. As a result, the complex elastic modulus at the bottom portion of the tread groove after vulcanization is high, and it is not possible to prevent the occurrence of cracks. It turned out to be enough.

The present applicant has already filed Japanese Patent Application No. Hei 7-26.
As shown in FIG. 11, when the tire is new, the portion b near the surface of the bottom of the tread groove a is used as shown in FIG.
(E * 1 / E * 2) between the complex elastic modulus E * 1 and the complex elastic modulus E * 2 of the inner portion c of the tread surface d, that is, the complex elastic modulus at the groove bottom portion. It has been proposed that by limiting the rise to 1.5 times or less the complex elastic modulus of the tread surface, it is possible to prevent cracks at the groove bottom for a long time.

[0009]

SUMMARY OF THE INVENTION The present inventor has set the ratio (E * 1 / E * 2) of the complex elastic modulus to be not less than 1.0 and not more than 1.5.
As a method for regulating below, for example, as shown in FIG. 12, uncured and small width ribbon-shaped rubber g2 is wound along a tread profile using a computer-controlled winding machine. It has been proposed to provide a concave portion e without applying a compressive force and then vulcanize in a mold.

[0010] However, the above-mentioned method complicates production equipment and is expensive. According to the present invention, the complex elastic modulus ratio (E
* 1 / E * 2) can be set to 1.0 or more and 1.5 or less, to prevent cracks that tend to occur at the bottom of the tread groove, and to prevent the appearance of the pneumatic tire from being deteriorated even after long-term use. It is intended to provide a manufacturing method.

[0011]

Means for Solving the Problems In the present invention, claim 1 is provided.
The described invention is a method of vulcanizing a raw tire cover having an unvulcanized tread rubber body in a mold provided with a groove projection for forming a groove, thereby forming a surface of a groove bottom of a tread groove formed. The ratio (E * 1 / E * 2) of the complex elastic modulus E * 1 of the vicinity portion to the complex elastic modulus E * 2 of the inner portion of the surface of the tread portion is 1.
A method of manufacturing a pneumatic tire for manufacturing a pneumatic tire having 0 or more and 1.5 or less, wherein the tread rubber body is extruded from a die plate and has a depth of the vulcanized tread groove. A recess having a width equal to or greater than the width of the recess is formed in the extruded portion of the die plate for extruding a tread rubber body. And a rubber guide portion having a width reduced and extending toward the upstream side of rubber extruding from the maximum width portion, and a tread rubber body is formed by passing through the formed protrusion. A method for manufacturing a pneumatic tire characterized by the following.

Further, the invention according to claim 2 is formed by vulcanizing a raw tire cover provided with an unvulcanized tread rubber body in a mold provided with a groove projection for forming a groove. Elastic modulus E * 1 near the surface at the bottom of the tread groove
Of a pneumatic tire for producing a pneumatic tire having a ratio (E * 1 / E * 2) of 1.0 or more and 1.5 or less with respect to the complex elastic modulus E * 2 of the inner portion of the surface of the tread portion. In the manufacturing method, the tread rubber body is extruded from a die plate, and a concave portion having a depth of 30% or more and 95% or less of a groove depth of the vulcanized tread groove is formed in the tread groove. A method for manufacturing a pneumatic tire, characterized in that the pneumatic tire is formed in accordance with a position, and is formed by cutting after extruding from a die plate without having a recess.

Further, the invention according to claim 3 is characterized in that the tread rubber body is 100 parts by weight of a rubber component of one or a combination of two or more of natural rubber, butadiene rubber, styrene butadiene rubber or isoprene rubber. 60 parts by weight or more and 100 parts by weight or less of carbon black;
And 0 or less by weight of a petroleum softener.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, according to the first and second aspects of the present invention, as shown in FIGS. 1 and 2, a tire raw cover 3 having an unvulcanized tread rubber body 2 is provided with a groove projection 4A for forming a groove.
The complex elastic modulus E * of the portion G near the surface of the bottom of the tread groove 5 formed by vulcanizing in the mold 4 provided with
1 and the complex elastic modulus E * of the inner portion S of the surface of the tread portion 6
This is a method for producing a pneumatic tire 1 for producing a pneumatic tire 1 having a ratio (E * 1 / E * 2) to 1.0 or more and 1.5 or less.

[0015] Pneumatic tire 1 manufactured according to the present invention
For example, as shown in FIG. 2, the tire is manufactured as a radial tire for a passenger car including a carcass 16 forming a skeleton of a tire and a belt layer 7 disposed radially outside the carcass 16 and inside the tread portion 6. Is done.

The carcass 16 has carcass cords arranged at an angle of 75 ° to 90 ° with respect to the tire equator C.
The carcass cord is composed of at least one carcass ply 16A, for example, a steel cord or nylon,
An organic fiber cord such as rayon or polyester can be preferably used.

The belt layer 17 includes at least one belt cord in which belt cords are arranged at an angle of about 10 ° to 35 ° with respect to the tire equator C, and in this embodiment, two inner and outer belt plies 17A whose cords cross each other. 17B. As the belt cord, similarly to the carcass cord, an organic fiber cord such as nylon, polyester, or rayon, and more preferably a high elastic cord such as steel can be appropriately used.

In this embodiment, the pneumatic tire 1 has a total of four tread grooves 5 linearly and continuously extending in the tire circumferential direction. This tread groove 5
The groove width GW measured on the surface of the tread portion is, for example, 5 mm or more and 20 mm or less, and the groove depth D is 5 mm or more and 18
It has a uniform depth of not more than mm and has the same cross-sectional shape as the groove projection 4A of the mold 4.

The tread rubber 6A of the tread portion 6
Is the ratio (E) of the complex elastic modulus E * 1 of the portion GD near the surface of the groove bottom of the tread groove 5 and the complex elastic modulus E * 2 of the inner portion S of the surface of the tread portion 6 when the tire is new.
* 1 / E * 2) is set to 1.0 or more and 1.5 or less.

Thus, the complex elastic modulus ratio (E * 1)
/ E * 2) in the range of 1.0 to 1.5,
Even after long-term use of the tire, it is possible to prevent the complex elastic modulus E * 1 at the groove bottom of the tread groove 5 from rising, and to prevent cracks over a long period of time.

When the complex modulus ratio exceeds 1.5,
There is no great difference from the conventional tire, and it is not possible to sufficiently prevent the early occurrence of cracks. Preferably the ratio is 1.0 to
1.25 is desirable. Note that the lower limit of the ratio is 1.
The reason why it is set to 0 is that it is ideal to make the complex elastic modulus the same because the rubber composition is the same.

The complex elastic modulus E * 2 of the inner portion S of the surface of the tread portion 6 varies depending on the rubber composition used.
In this example, it is set to about 5.0 to 5.5 (MPa).

In the present invention, the complex elastic modulus is determined by measuring the portion G of the tread rubber 6A in the vicinity of the surface of the bottom of the tread groove 5 in the tread rubber 6A when the tire is fully heat-removed.
4mm width x 30mm at 1mm inside position from groove bottom surface
Cut out a strip sample of length x 1.5mm thickness,
A sample of the same size was cut out at the same or deeper position as the inner portion S of the surface of the tread portion, and a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. was used. It is defined as a value measured under the condition of strain ± 2%.

In such a pneumatic tire 1, the carcass ply 16A is inflated in a toroidal shape on the tire forming drum, and the belt plies 17A and 17B are provided at positions corresponding to the tread portions, and furthermore, the belt plies 17A and 17B are provided radially outward. It is obtained by vulcanizing in a mold 4 the raw tire cover 3 to which the vulcanized tread rubber body 2 is attached.

According to the first aspect of the present invention, the unvulcanized tread rubber body 2 is, for example, as shown in FIG.
As shown in FIG. 4, it is formed by being continuously extruded from a die plate 8 composed of an upper die 8A provided with a molding projection 9 and a lower die 8B having a flat surface F in a belt shape.

The tread rubber body 2 has a depth d (shown in FIG. 1) of 30% of the groove depth D of the tread groove 5 after vulcanization.
% Or more and 95% or less of the concave portion 7 must be formed in advance in accordance with the position of the tread groove 5.

If the tread rubber body 2 has no recess 7 or if the depth of the recess 7 is less than 30% of the depth of the tread groove 5 after vulcanization, vulcanization is performed. Occasionally, a large compressive force is easily received from the groove protrusion 4A for forming the groove, and this promotes an increase in the complex elastic modulus at such a portion.

Conversely, the depth of the recess 7 of the tread rubber body 2 is
When it exceeds 95% of the groove depth of the tread groove 5,
The formation of the tread groove 5 becomes difficult.

Preferably, the depth d of the concave portion 7 is about 40 to 80% of the groove depth D of the vulcanized tread groove 5,
In this example, a case of about 50% is illustrated. The width W of the recess 7 is 100% of the groove width GW of the tread groove 5.
It is preferable that the width is as wide as about 150%.

As shown in FIG. 1, when the toroidal raw tire cover 3 is vulcanized, the concave portion 7 and the groove projection 4A for forming the groove of the vulcanizing mold 4 substantially coincide with each other. Thus, by being provided in accordance with the position of the tread groove 5, the compression force received from the groove protrusion 4A for forming the groove of the mold 4 during vulcanization can be reduced, and thereby the portion of the tread groove 5 near the groove bottom can be obtained. Can be prevented from increasing.

The tread rubber body 2 is formed as a flat surface by making the outer surfaces of the convex portions 13 disposed between the concave portions 7 and 7 have the same height, and two planes intersect as in this embodiment. Various shapes such as those formed in a mountain shape can be adopted.

Next, as shown in FIG. 5 where the die plate 8 is viewed from the lower die 8B side, the recess 7 is
A maximum width portion 10 having a width equal to the width W of the concave portion 7 and a rubber guide portion 11 extending from the maximum width portion 10 toward the upstream side of the rubber extruding portion. Is formed, and the tread rubber body 2 is formed by passing through the formed protrusion 9.

Generally, as shown in FIG. 9, in a conventional die plate D, a molding projection 21 provided on an upper die 20A has a uniform width dimension and a lower die 20B which is directed toward the rubber extrusion upstream side. The molding surface 21A is inclined at an angle α so as to increase the distance between the molding surfaces 21A.

However, in the case where the molding protrusions 21 are in such a shape, the extruded rubber is not covered with the molding protrusions 21.
And it is easy to dive into between the lower mold 20B, and eventually,
It is probable that the compressive force acting on the rubber was increased in this portion, resulting in an increase in the complex modulus after vulcanization.

On the other hand, the molded projection 9 according to the present embodiment
Then, as shown by the arrow in FIG. 5, the raw rubber extruded from the upstream side is branched to the width direction both sides of the molding projection 9 with the rubber guide portion 11 as a boundary, and is extruded while flowing to the downstream side. Can be.

Accordingly, it is possible to reduce the rubber penetration between the molding surface 9A facing the lower mold 8B of the molding projection 9 and the flat surface F of the lower mold 8B. Can be prevented from increasing. Such a tread rubber body 2 can suppress an increase in complex elastic modulus at a groove bottom portion of the tread groove 5 even after vulcanization.

The present inventors vulcanized three types of tread rubber bodies 2 having different depths of the concave portions manufactured by the die plate 8 of the present embodiment in a vulcanizing can and examined the complex elastic modulus of each part. . In this case, unlike the vulcanizing mold, the compressive force at the time of vulcanization does not act, but the effect of the compressive force acting on the tread rubber body 2 through the die plate 8 is different from the case of vulcanizing with the mold. It is also considered comparable.

As a result of the test, the ratio between the complex elastic modulus of the portion near the bottom of the concave portion 7 and the complex elastic modulus of the inner portion of the surface of the convex portion 13 is 1.25 or less. A good result of almost the same, such as 1.07, was obtained. In the case of the tread rubber body manufactured by the conventional die plate D shown in FIG. 9, the ratio of the complex elastic modulus was about 1.71. The cut-out position of the sample conforms to the case described above.

Next, it is more preferable that, for example, the rubber protrusion 11 is tapered and pointed toward the upstream side of the rubber extrusion, but the present invention is not limited to this. 6A and 6B show another embodiment of the molding projection 9, in which FIG. 6A is a triangular shape, and FIGS.
A rubber guide portion 11 having both side surfaces formed of curved surfaces,
(D) shows the two-stage rubber guide portion, but may be variously modified such as a rubber guide portion 11 having a semicircular shape.

As a result of the provision of the rubber guide portion 11, the molding projection 9 is sufficiently effective even when the molding surface 9A is inclined as in the prior art. It is desirable that the distance h (shown in FIG. 5) between the lower die 8B and the flat surface F be substantially constant. The molded projections 9 of the present embodiment may be formed by polishing the projections of an existing die plate, for example, so that existing production facilities can be used as they are and can be made inexpensively.

Next, the invention according to claim 2 will be described. In the invention according to claim 2, the tread rubber body 2
Is extruded from the die plate and is formed so that the concave portion 7 whose depth is 30% or more and 95% or less of the groove depth of the vulcanized tread groove 5 is aligned with the position of the tread groove 5. They are common in points.

However, the tread rubber body 2 is
As shown in FIG. 5, the resin is extruded from the die plate 14 having no molding projections, and is extruded without having the above-mentioned concaves.
Is formed. The description of the recess 7 is as described in the description of the first aspect of the present invention.

The present inventors have developed an unvulcanized tread rubber body 2
Further, it has been confirmed by an experiment that when the concave portion 7 is formed by cutting, the complex elastic modulus E * 1 in the bottom inner portion of the tread groove 5 does not increase after vulcanization.

Incidentally, "without the concave portion 7" means
In addition to the case where no concave portion is provided, the case where a small concave portion of less than 30% of the depth D of the tread groove 5 is provided is included. Such a case is preferable in that the shaving amount by cutting can be reduced.

In addition, such cutting is performed by the tread rubber body 2 continuously extruded from the die plate 14 in a band shape.
Immediately after extrusion, the tread rubber body 2 cut to a predetermined size is wound around the outer periphery of a drum 15 that can be sufficiently cooled and rotated, as shown in FIG. 8, in addition to shaving using a cutting tool (grouping tool) or the like. Alternatively, the cutting tool T having the fixed cutting tool M can be pressed against the tread rubber body 2. In addition, the scraped rubber is again
It can be put into an extruder and reused. In addition, when a plurality of tread rubber bodies formed by this method were vulcanized in a vulcanizing can in the same manner as described above, the complex elastic modulus near the bottom of the concave portion and the complex elastic modulus inside the surface of the convex portion 13 were determined. , A good result of 1.25 or less was obtained.

Further, according to the second aspect of the present invention, when the tread groove 5 is bent in a zigzag manner, or when the tread groove 5 is a lateral groove extending in the tire axial direction, and cannot be formed by extrusion, It can be particularly preferably implemented,
Similarly to the first aspect of the present invention, the production equipment can be prevented from becoming complicated and can be manufactured at low cost.

Although the two methods have been described above, in the present example, the tread rubber body 2 disposed radially outside the belt layer is formed with a substantially uniform composition as a whole. And various rubber compositions conventionally used can be adopted.

For example, a rubber component 10 obtained by mixing a polymer of one or a combination of two or more of natural rubber, butadiene rubber, styrene butadiene rubber and isoprene rubber.
A tire is manufactured by using the above-mentioned method by employing a rubber composition in which 60 parts by weight or more and 100 parts by weight or less of carbon black and 30 parts by weight or less of a petroleum softening agent are blended with respect to 0 part by weight. This is effective in preventing the occurrence of cracks.

In general, passenger car tires, especially 60%
The tread rubber of the high performance tire flattened below
A rubber composition containing a relatively large amount of a petroleum softening agent and having a large complex elastic modulus is often used from the beginning.

Therefore, in such a tread rubber, the antiaging agent, oil, and the like migrate toward the belt layer 7 due to aging, so that the degree of increase in the complex elastic modulus is large and the crack resistance is poor. It is also known.

Therefore, the change in the complex modulus can be reduced by limiting the amount of the petroleum softening material such as paraffin, naphthene or aromatic to a small amount of 30 parts by weight or less. In the first place, the softening agent facilitates the processing operation of the rubber at the time of manufacture rather than the tire running performance, so it can be configured so as not to be added at all, but when added, about 10 to 30 parts by weight is added. desirable.

[0052]

EXAMPLE A tire having a tire size of 205 / 55R15 and having a structure as shown in FIG. 2 was manufactured on a trial basis by the following method, and its crack resistance and the like were tested. Examples 1 and 2, Comparative Example 1 An unvulcanized tread rubber body extruded with a die plate shown in FIG.
This was molded with a vulcanizing mold. Examples 3 and 4 and Comparative Example 2 An unvulcanized tread rubber body having a concave portion cut out after being extruded with a die plate shown in FIG. It was molded with a metal mold. Conventional Example A tread rubber body extruded with a conventional die plate shown in FIG. 9 was mounted on a tire tire cover having a radial structure, and this was molded with a vulcanizing mold. The internal structure of each sample tire, tread pattern, rubber composition of the tread rubber,
In each case, the same thing is adopted, and there is no influence of these. The test method is as follows.

A) Complex elastic modulus For each test tire, when the tire is new and after heat aging (described later), the complex elastic modulus E * 1 of the inner portion G of the surface of the bottom of the tread groove in the tread rubber and the tread portion The complex elastic modulus E * 2 of the inner portion G2 of the surface is cut out as a strip sample of 4 mm width × 30 mm length × 1.5 mm thickness at a position 1 mm inward from the surface portion, and a viscoelastic material manufactured by Iwamoto Seisakusho Co., Ltd. is cut out. The measurement was performed using an elastic spectrometer under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%.

B) Ozone test The test tire was aged for 10 days in an oven at 70 ° C., and then assembled on a regular rim (internal pressure 2.3 kgf / c).
m ² ) and left in an ozone chamber with an ozone concentration of 50 pphm to observe the state of cracks in the tread groove. The evaluation is as follows. ：: No cracks were generated at all. △: Wrinkles or fine cracks were generated. ×: Apparent cracks were formed and the appearance was impaired.

[0055]

[Table 1]

As a result of the test, each of the tires of the examples has a small complex elastic modulus E * 1 inside the groove bottom at the time of a new article, and is smaller than the other comparative tires even if the tire becomes highly elastic due to heat aging. Was confirmed. And based on this,
Regarding the crack resistance, it was confirmed that no crack was generated for two weeks or more even in a severe environment such as an ozone chamber. After a lapse of one month, slight cracking had begun to occur, but the appearance had not been spoiled.

Conversely, in the tires of Comparative Examples 1 and 2, the complex elastic modulus has already increased at the bottom of the groove after vulcanization, and in each case, fine cracks have been formed after two weeks. Many obvious cracks were generated, and the appearance was significantly impaired.

[0058]

As described above, according to the present invention, the ratio of the complex elastic modulus between the inner portion of the tread groove and the inner portion of the tread surface can be reduced without making the production equipment complicated and expensive. 1.
0 to 1.5, air that can prevent cracks from occurring at the groove bottom portion by suppressing the rubber from being highly elastic at the groove bottom portion of the tread groove, and maintain an aesthetic appearance over a long period of time. Tires can be manufactured.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a raw tire cover.

FIG. 2 is a partial sectional view of a tire showing an embodiment of the present invention.

FIG. 3 is a sectional view showing an example of a die plate.

FIG. 4 is a perspective view showing a tread rubber body.

FIG. 5 is a perspective view of a molding protrusion.

FIGS. 6A to 6D are cross-sectional views showing another example of the molding protrusion.

FIG. 7 is a sectional view showing another example of a die plate.

FIG. 8 is a perspective view showing another embodiment of the present invention.

FIG. 9 is a perspective view for explaining a conventional molding protrusion.

FIG. 10 is a sectional view showing a conventional tread rubber body and a die plate.

FIG. 11 is a partial sectional view of a tread portion.

FIG. 12 is a cross-sectional view illustrating a method for manufacturing a conventional pneumatic tire.

[Explanation of symbols]

 2 Tread rubber body 3 Tire raw cover 4 Mold 4A Groove protrusion for groove formation 5 Tread groove 6 Tread portion 6A Tread rubber 7 Concave 8 Die plate 9 Molding protrusion 10 Maximum width portion 11 Rubber guide portion G Tread groove groove bottom S inside the surface of the tread (land) E * 1, E * 2 Complex elastic modulus

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B29K 21:00 (56) References JP-A-56-144948 (JP, A) JP-A-62-77929 (JP, A) JP-A-61-228941 (JP, A) JP-A-4-53735 (JP, A) JP-A-9-104205 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29D 30 / 52 B29C 47/08-47/16 B29B 11/10-11/14 B60C 1/00 B60C 11/00-11/04 C08L 7/00-9/08

Claims (3)

(57) [Claims] 1. A surface of a bottom of a tread groove formed by vulcanizing a raw tire cover having an unvulcanized tread rubber body in a mold provided with a groove projection for forming a groove. The ratio (E * 1 / E * 2) of the complex elastic modulus E * 1 of the vicinity portion and the complex elastic modulus E * 2 of the inner portion of the surface of the tread portion is set to 1.0.
A pneumatic tire manufacturing method for manufacturing a pneumatic tire having the above and 1.5 or less, wherein the tread rubber body is extruded from a die plate, and has a depth of the tread groove after the vulcanization. A recess of 30% or more and 95% or less of the groove depth is formed in accordance with the position of the tread groove, and the recess has a width equal to the width of the recess in the extruded portion of the die plate for extruding a tread rubber body. A molding projection consisting of a maximum width portion and a rubber guide portion extending from the maximum width portion toward the upstream side of rubber extruding with a reduced width is provided, and the tread rubber body is formed by passing through the molding projection. A method for manufacturing a pneumatic tire, which is a feature. 2. The surface of the bottom of a tread groove formed by vulcanizing a raw tire cover having an unvulcanized tread rubber body in a mold provided with a groove projection for forming a groove. The ratio (E * 1 / E * 2) of the complex elastic modulus E * 1 of the vicinity portion and the complex elastic modulus E * 2 of the inner portion of the surface of the tread portion is set to 1.0.
A pneumatic tire manufacturing method for manufacturing a pneumatic tire having the above and 1.5 or less, wherein the tread rubber body is extruded from a die plate, and has a depth of the tread groove after the vulcanization. A recess not less than 30% and not more than 95% of the groove depth is formed in alignment with the position of the tread groove, and this recess is formed by being extruded from the die plate without having a recess, and then formed by cutting. A method for manufacturing a pneumatic tire, which is a feature. 3. The rubber composition according to claim 1, wherein said tread rubber body is at least 60 parts by weight and at least 100 parts by weight based on 100 parts by weight of a rubber component of one or a combination of natural rubber, butadiene rubber, styrene butadiene rubber and isoprene rubber. The method for producing a pneumatic tire according to claim 1 or 2, comprising the following carbon black and 30 parts by weight or less of a petroleum softening material.