JP6719726B2 - Pneumatic tire manufacturing method, rubber material and pneumatic tire - Google Patents

Description

The present invention relates to a method for manufacturing a pneumatic tire having an outer apex structure, a rubber material for the outer apex structure, and a pneumatic tire.

In recent years, a pneumatic tire having an outer apex structure has been proposed as a pneumatic tire having a structure capable of realizing weight reduction without lowering rigidity and durability. In this tire having an outer apex structure, the outer apex, which is a high-strength rubber member containing a thermosetting resin, is arranged between the bead apex and the sidewall (Patent Document 1).

As a method of molding a tire having this outer apex structure, after preliminarily joining the extruded outer apex and the sidewall, a method of sticking to the rolled carcass ply or an outer apex to the rolled carcass ply. And there is a method to attach the side wall one by one. Generally, in order to shorten the cycle time of the molding process, the former method of preliminarily joining the outer apex and the sidewall is mainly adopted.

JP, 2013-129346, A

However, even when any of the above-mentioned methods are used, a step is generated in the joint portion between the rubber members such as the outer apex and the side wall, and air is accumulated in this step, so that the tire after manufacturing has a defect. There was a risk of this occurring.

For example, when the outer apex and the sidewall are pre-joined to each other, the rubber material 20 as shown in FIG. 3 is obtained. However, the sticking accuracy at this time has a variation of about ±3 mm, and the rubber material 20 obtained by the joining. A step may occur at the joint between the outer apex 1 and the sidewall 2.

It should be noted that reference numeral 3 in FIG. 3 is a clinch apex, and when such a member is also joined, a step may occur between this member and another rubber member.

Therefore, the present invention, when manufacturing a pneumatic tire of the outer apex structure, between the outer apex and the sidewall, to prevent the occurrence of a step between the clinch apex, defect to the manufactured tire. It is an object to provide a technology that can prevent the occurrence of

The invention according to claim 1 is
Outer apex containing a thermosetting resin is a method for producing a pneumatic tire for producing a pneumatic tire having an outer apex structure disposed between a bead apex and a sidewall,
By extruding the outer apex and the sidewall at the same time, the outer apex and the sidewall are molded into a rubber material that is integrated without a step between them,
The volume ratio of the outer apex to the sidewall is 10 to 15% by volume,
The durometer hardness of the outer apex is 25 to 35 higher than the durometer hardness of the sidewall,
The method for producing a pneumatic tire is characterized in that the outer apex has a Mooney viscosity higher than that of the sidewall by 20 to 30.

The invention according to claim 2 is
The method for producing a pneumatic tire according to claim 1 , wherein the outer apex has a durometer hardness of 78 to 88 and a Mooney viscosity of 58 to 68.

According to the present invention, when manufacturing a pneumatic tire having an outer apex structure, a step is prevented from occurring between the outer apex and the side wall, and further between the clinch apex, and a defect is produced on the manufactured tire. It is possible to provide a technique capable of preventing the occurrence of

FIG. 3 is a cross-sectional view of a rubber material for an outer apex structure obtained in the pneumatic tire manufacturing method according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view near a bead portion of a pneumatic tire manufactured by the method for manufacturing a pneumatic tire according to the first embodiment of the present invention. It is sectional drawing of the rubber material obtained by the conventional method.

Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

1. First Embodiment FIG. 1 is a cross-sectional view of a rubber material for an outer apex structure obtained by a method for manufacturing a pneumatic tire according to a first embodiment.

In the method for manufacturing a pneumatic tire according to the first embodiment, an outer apex and a side wall 2 as shown in FIG. 1 are integrally formed by extrusion-molding the outer apex and the side wall at the same time. A rubber material for an apex structure (hereinafter, also simply referred to as “rubber material”) 10 is formed.

As a result, unlike the conventional technique of joining the separately-extruded outer apex 1 and the sidewall 2 as shown in FIG. 3, the outer apex 1 and the sidewall 2 of the rubber material 10 after being formed are separated from each other. There is no step between them. As a result, it is possible to prevent the occurrence of defects due to the accumulation of air in the portion where the step is generated.

Hereinafter, the extrusion molding of the outer apex and the sidewall in the pneumatic tire manufacturing method according to the present embodiment will be described. In the present embodiment, the clinch apex 3 is also extruded at the same time to form the rubber material 10 in which the outer apex 1, the sidewall 2 and the clinch apex 3 are integrated.

A multi-layer extruder equipped with a preformer is used for molding the rubber material 10 shown in FIG.

Specifically, first, in each rubber flow channel of a multi-layer extruder having three rubber flow channels, a rubber compounded for the outer apex 1, a rubber compounded for the sidewall 2, and a clinch apex. Supply rubber with the composition for 3.

The rubber supplied to each rubber flow path is sent to the preformer attached to the tip of the multilayer extruder. The preformer guides the respective rubbers sent from the multi-layer extruder to the positional relationship shown in FIG.

Then, the outer apex 1 in which the outer apex 1, the side wall 2, and the clinch apex 3 are integrated in the positional relationship shown in FIG. 1 is formed by extrusion molding so that the respective rubbers are integrated at the discharge port. The rubber material 10 for the structure is obtained.

As described above, by using the multi-layer extruder and the preformer to extrude the rubber material 10 in which the outer apex 1, the sidewall 2 and the clinch apex 3 are integrated, the separately extruded rubber members are formed. Unlike the conventional technique of joining (see FIG. 3 ), the outer apex 1, the sidewall 2, and the clinch apex 3 can be flattened without causing a step at each boundary.

Then, when a pneumatic tire is manufactured using such a rubber material 10, a pneumatic tire as shown in FIG. 2 can be manufactured. In FIG. 2, 4 is a bead core, 5 is a bead apex, 6 is a carcass ply, 7 is an inner liner, and 8 is a chafer.

This pneumatic tire is manufactured by attaching the rubber material for the outer apex structure obtained by the above-mentioned integral extrusion molding to the carcass ply 6 outside the bead apex 5 and then performing vulcanization molding. To be done.

In the present embodiment, as described above, since a step is prevented from being generated at the boundary between the outer apex 1, the sidewall 2 and the clinch apex 3, the pneumatic tire as shown in FIG. 3 is manufactured. At this time, air is not accumulated between the outer apex 1, the side wall 2, and the other rubber members adjacent to the clinch apex 3, and it is possible to prevent the occurrence of a defect in the manufactured tire. ..

In the present embodiment, the case where three types of rubber members of outer apex 1, side wall 2, and clinch apex 3 are extruded at the same time has been described, but the present invention is not limited to this, and four or more types of rubber members are used. The members may be extruded at the same time. Even in such a case, since it is possible to prevent a step from being generated at the boundary between the rubbers, it is possible to prevent an air accumulation from occurring in the tire after manufacturing.

2. Second Embodiment A method for manufacturing a pneumatic tire according to a second embodiment is an outer apex in which an outer apex 1 and a sidewall 2 are integrated as in the above-described first embodiment. When molding the structural rubber material 10, the outer apex in which the volume ratio of the outer apex 1 to the side wall 2, the hardness difference and the viscosity difference between the side wall 2 and the outer apex 1 are adjusted to predetermined values. 1 is used.

As a result, when a nonstandard product such as a dimension shortage or a production residue occurs in the molding of the rubber material 10 for the outer apex structure, the rubber material 10 for the outer apex structure is mixed with the rubber for the sidewall 2. It can be reused as it is.

Hereinafter, a method for manufacturing the pneumatic tire according to the second embodiment will be described. In the following description, the present embodiment will be described in detail after describing the problems that the conventional technology has regarding reuse of rubber.

In the general pneumatic tire manufacturing process, if non-standardized products such as insufficient dimensions or production residuals occur in the molded sidewall, return it to the mixing process to create rubber for the sidewall and create it. By reusing it with the rubber inside, we are suppressing the increase in damage.

However, in manufacturing a pneumatic tire having an outer apex structure, if other rubber members such as an outer apex are preliminarily joined to the sidewall as shown in FIG. It cannot be returned to the mixing process as it is.

For example, outer apex contains a thermosetting resin to improve strength, and even if you try to mix such outer apex with rubber for sidewalls, the rubber will not mix well, so it will be dispersed. breaking bad. When a tire is manufactured by using a rubber having such a poor dispersion, cracks occur at the interface between the undispersed rubbers and the durability is significantly reduced, resulting in a waste tire.

Therefore, conventionally, when reusing the rubber material in which the sidewall and the outer apex are previously joined, it is necessary to manually separate the sidewall and the outer apex using an organic solvent such as naphtha, It was a factor that hindered productivity. Further, in recent years, it has been required to reduce the amount of organic solvent used at the production site, and there is a problem from this viewpoint as well.

The problem of reuse in manufacturing the tire having the outer apex structure may still occur in the method for manufacturing the pneumatic tire according to the first embodiment described above. For this reason, the present inventor repeated various experiments and studies on a technique that allows the rubber material for the outer apex structure obtained in the above-described embodiment to be reused as it is, and the air according to the present embodiment. A method for manufacturing a filled tire has been found.

That is, the present inventor, by appropriately adjusting the volume ratio of the outer apex to the side wall, and the hardness difference and the viscosity difference between the side wall and the outer apex, the side wall and the outer apex are integrated. It was found that the rubber material can be reused as it is in the mixing process of the rubber for the sidewall.

Specifically, in the pneumatic tire manufacturing method according to the present embodiment, the volume ratio of the outer apex to the sidewall is set to 10 to 15% by volume, and the durometer hardness of the outer apex is higher than the durometer hardness of the sidewall. It is characterized by increasing the Mooney viscosity of the outer apex by 20 to 30 higher than that of the sidewall.

In the present specification, the durometer hardness is a value measured using a durometer type A after vulcanizing rubber at 165°C, and the Mooney viscosity is a value measured according to JIS K 6300-1.

By using the outer apex with such a composition, even if the rubber material for the outer apex structure after being integrated by extrusion molding is returned as it is to the mixing process of the rubber for the side wall, poor dispersion occurs. Can be properly reused without doing.

If the volume ratio of the outer apex to the sidewall is not within the range of 10 to 15% by volume, poor dispersion may occur, and if it is less than 10% by volume, the tire has insufficient rigidity and durability. If it exceeds 15% by volume, the weight of the tire becomes too large and rolling resistance may be deteriorated.

Further, if the difference in durometer hardness between the outer apex and the sidewall is less than 25, the rigidity and durability of the tire may be insufficient, and if it exceeds 35, poor dispersion in the mixing step may occur. It may occur.

Further, when the difference in Mooney viscosity between the outer apex and the side wall is less than 20, the rigidity and durability of the tire may be insufficient, and when it exceeds 30, dispersion failure occurs in the mixing step. There is a risk of

The outer apex preferably has a durometer hardness of 78 to 88 and a Mooney viscosity of 58 to 68, while satisfying the above-described condition of the difference from the sidewall. In this case, a tire having higher rigidity and durability can be manufactured.

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

1. Test Example (1) Test Examples 1 to 8
As in the above-described first embodiment, the outer apex and the side wall are extrusion-molded at the same time to create a rubber material for the outer apex structure as shown in FIG. Tires were produced (Test Examples 1 to 8).

Further, in Test Examples 1 to 8, as shown in Table 1, the volume ratio of the outer apex to the sidewall, the durometer hardness, and the Mooney viscosity were made different. For the sidewall, the rubber having the same composition as in Test Examples 1 to 8 (durometer hardness 53, Mooney viscosity 38) was used.

(2) Test example 9
As in the conventional method, the extruded outer apex and the side wall were joined together to produce the rubber material shown in FIG. 3, and a pneumatic tire was produced using this rubber material. The volume ratio of the outer apex to the sidewall of Test Example 9, the durometer hardness, and the Mooney viscosity were set to the same conditions as in Test Example 1.

2. Evaluation (1) Occurrence of air traps The cross sections near the bead portions of the pneumatic tires manufactured in Test Examples 1 to 9 were visually observed to evaluate whether air traps were generated inside. The results are shown in Table 1.

(2) Evaluation of Reuse Each of the rubber materials obtained in Test Examples 1 to 9 was returned to a Banbury mixer having a capacity of 270 L, and reused by mixing with rubber for a sidewall. Then, the following items were evaluated when manufacturing a pneumatic tire using the obtained sidewall rubber.

(A) Dispersed state The sidewall rubber obtained by reuse is made into a sheet, and it is visually confirmed whether or not burnt rubber lumps are generated due to poor dispersion, and the curast data at random 10 points is sampled. (ML: minimum torque value, MH: maximum torque value, T10: time until the torque increases from ML by 10% when the difference between the maximum torque value and the minimum torque value (MH-ML) is 100%, T90: When the difference between the maximum torque value and the minimum torque value (MH-ML) is 100%, the time until the torque rises 90% from ML) is measured, and the measurement result is within the standard range of the rubber for the sidewall. It was evaluated whether it fits in or not.

Then, if good results were obtained for both the visual confirmation and the evaluation result of the curast data, it was set as “good”, and if there was a problem in either one, it was set as “OK” and both If the two matched, it was designated as "impossible".

(B) Rigidity/Durability The tire after manufacturing was subjected to a tire general durability test using a drum tester for durability evaluation. In this test, a tire is made to run on a drum under conditions of prescribed air pressure, load, and speed, and a running distance in an undamaged state is measured. The rigidity and durability of each tire were evaluated based on the measurement results. The values in the table are values with Test Example 1 set to 100.

(C) Tire Weight The weight of each manufactured tire was measured, and the weight of each tire was evaluated based on the measurement results. The values in the table are values with Test Example 1 set to 100.

In Test Examples 1 to 8 using the rubber material in which the sidewall and the outer apex are simultaneously extruded and integrated, in any of the test examples, air accumulation due to a step between the sidewall and the outer apex was observed. It did not occur, and it was confirmed that the occurrence of defects was appropriately prevented.

Further, in Test Examples 2 to 8 in which the hardness difference and the viscosity difference between the outer apex and the side wall, and the volume ratio of the outer apex to the side wall were adjusted to appropriate values, the side wall and the outer apex were It was found that even if the integrated rubber material was returned to the sidewall mixing step, the dispersion failure did not occur and the rubber material could be appropriately reused.

Then, when the hardness difference and the viscosity difference between the outer apex and the side wall, and the volume ratio of the outer apex to the side wall are adjusted to the values as in Test Examples 2 to 4, the tire rigidity/durability and weight are adjusted. From the point of view, it was found that a preferable pneumatic tire can be manufactured by using a reuse material.

Although the present invention has been described above based on the embodiment, the present invention is not limited to the above embodiment. Various modifications can be made to the above-described embodiments within the same and equivalent scope as the present invention.

1 Outer Apex 2 Sidewall 3 Clinch Apex 4 Bead Core 5 Bead Apex 6 Carcass Ply 7 Inner Liner 8 Chafer 10, 20 Rubber Material

Claims (2)

Outer apex containing a thermosetting resin is a method for producing a pneumatic tire for producing a pneumatic tire having an outer apex structure disposed between a bead apex and a sidewall,
By extruding the outer apex and the sidewall at the same time, the outer apex and the sidewall are molded into a rubber material that is integrated without a step between them,
The volume ratio of the outer apex to the sidewall is 10 to 15% by volume,
The durometer hardness of the outer apex is 25 to 35 higher than the durometer hardness of the sidewall,
The method of manufacturing a pneumatic tire, wherein the Mooney viscosity of the outer apex is 20 to 30 higher than the Mooney viscosity of the sidewall. The method for producing a pneumatic tire according to claim 1 , wherein the outer apex has a durometer hardness of 78 to 88 and a Mooney viscosity of 58 to 68.

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