JP2011235819A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire formed by substituting raw materials originated from resources except oil for a part or the whole of a clinch rubber.SOLUTION: In this pneumatic tire 1 using a rubber composition for a clinch, a bead apex rubber 8 includes an apex main part 8A tapered and extended outward in the radial direction and has a nearly triangle cross section, and the height La of the apex main part 8A is 25 mm or less. The thickness of the clinch rubber as the minimum thickness from an inside surface of the clinch rubber 9 positioning outside in the radial direction than the outer end of the apex main part in the radial direction among the inside surface of the clinch rubber 9 inside in the tire axial direction to an exposed outside surface among the outside surface of the clinch rubber 9 outside in the tire axial direction is 5.0 mm or more, the hardness of the clinch rubber 9 is 75 or more, the total content of a natural rubber and a reformed natural rubber is 70 mass% or more based on 100 mass% of rubber component, and the content of silica is 50 mass% or more based on 100 mass% of a reinforcing filler.

Description

The present invention relates to a pneumatic tire.

A side surface (side) portion of a general pneumatic tire is divided into a portion where the tire bends (side wall portion) and a portion which contacts the rim. The clinch rubber located at the portion in contact with the rim is required to have good chafing performance (rubber wear resistance when the tire and the rim are rubbed). Therefore, conventionally, a large amount of carbon black having a specific surface area of a certain level or more has been blended in the clinch rubber in order to blend natural rubber with a butadiene rubber having good wear resistance and further improve the wear resistance. . Thus, conventionally, a large amount of butadiene rubber and carbon black, which are raw materials derived from petroleum resources, have been used for clinch rubber in order to obtain good chafing performance.

However, in recent years, environmental issues have become more important and regulations on carbon dioxide emissions have been strengthened. In addition, since oil reserves are limited, the use of raw materials derived from petroleum resources is limited. This environment-oriented orientation is no exception in the tire field, and there is an increasing demand to replace some or all of the petroleum-derived raw materials currently used with raw materials derived from non-oil resources. There is an increasing demand for rubber compositions.

Eco tires using silica or the like as an alternative raw material for carbon black have been developed (for example, Patent Document 1). However, in a rubber composition for clinching, if a large amount of natural rubber is blended instead of butadiene rubber, which is a synthetic rubber, or if a white filler such as silica is blended instead of carbon black, it can be used in a heavy-duty passenger car. Under traveling conditions with high severity such as when used, chafing may occur, resulting in rim displacement or deterioration in durability. In order to solve such a problem, a method of improving the wear resistance by adding a large amount of silica as a reinforcing filler can be considered. However, when a large amount of silica is blended, the rubber hardness becomes very high, and there is a problem that it is difficult to assemble the rim. There is also room for improvement in the chafing performance. Thus, when a part or all of raw materials derived from petroleum resources of clinch rubber are replaced with raw materials derived from resources other than petroleum, the present situation is that good chafing performance is not obtained.

JP 2007-169431 A

The present invention solves the above-mentioned problem and provides a pneumatic tire that can obtain good chafing performance even when a part or all of raw materials derived from petroleum resources of clinch rubber are replaced with raw materials derived from resources other than petroleum. The purpose is to provide.

As a result of intensive studies, the inventors of the present invention have a high rubber hardness when a large amount of silica is blended, so that when a load is applied, there is little deformation between the rim and the clinch rubber, and a shear force between the rim and the clinch rubber. This led to the hypothesis that chafing performance would deteriorate. The following invention has been completed based on the hypothesis that good shearing performance can be obtained by relaxing the shearing force generated by deformation of the clinch rubber.
That is, the present invention is disposed on the outer side in the tire axial direction of the carcass extending from the tread portion to the bead core of the bead portion to the bead core, the bead apex rubber extending radially outward from the bead core, and the bead apex rubber. And a bead apex rubber having a substantially triangular apex section extending in a radially outward direction from the bead core, and a bead apex rubber having a clinch rubber forming an outer surface of the bead portion. The apex main portion height La in the radial direction from the bead base line at the radially outer end of the apex main portion is 25 mm or less, and the inner surface of the clinch rubber on the inner side in the tire axial direction is outside the apex main portion in the radial direction. From the inner surface located radially outward from the end, the clinch rubber tire axial direction Of the outer outer surfaces, the clinch rubber thickness, which is the minimum thickness to the exposed outer surface, is 5.0 mm or more, the hardness of the clinch rubber is 75 or more, and the clinch rubber has a rubber component of 100 mass. The total content of natural rubber and modified natural rubber is 70% by mass or more, and the silica composition in 100% by mass of the reinforcing filler is 50% by mass or more. It is related with the pneumatic tire currently manufactured.

The bead apex rubber is composed of the apex main portion and a wing portion that extends to the apex main portion and extends radially outward, and is more radially outward than the radially outer end of the apex main portion of the clinch rubber. It is preferable that the carcass is positioned between the positioned inner surface and the wing portion.

It is preferable that the silica has a nitrogen adsorption specific surface area of 50 to 300 m ² / g.

In the rubber composition for clinch, it is preferable that the content of the silica is 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are specified in a 5% internal pressure state in which the tire is assembled on a regular rim and filled with air so as to be 5% of the regular internal pressure. Value. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, JATMA is a standard rim, TRA is “DESIGN Rim”, If it is ETRTO, it means “MEASURING Rim”. The “regular internal pressure” is the air pressure defined by the tire for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFRATION PRESURES” for TRA. In the case of ETRTO, it means “INFLATION PRESURE”, but in the case of a passenger car tire, it is 180 kPa. Further, the “bead base line” means a tire axial direction line passing through a rim diameter position defined by the standard.

The clinching rubber used in the present invention is a clinching rubber composition in which the total content of natural rubber and modified natural rubber is a specific amount or more and the silica content in the reinforcing filler is a predetermined amount or more. A part or all of raw materials derived from petroleum resources of clinch rubber have been replaced with raw materials derived from resources other than petroleum. Therefore, it is possible to reduce the ratio of raw materials derived from petroleum resources, to prepare for the depletion of raw materials derived from petroleum resources, and to consider the environment. Further, even when such a clinch rubber is used, (I) a radial direction from the bead base line of the radially outer end of the apex main portion having a substantially triangular cross section extending outwardly in the radial direction from the bead core. The apex main portion height La is set to a specific value or less, and (II) of the inner surface of the clinch rubber in the tire axial direction, from the inner surface located radially outward from the radially outer end of the apex main portion. By setting the clinch rubber thickness, which is the minimum thickness to the exposed outer surface, of the outer surface of the clinch rubber in the tire axial direction outer side to a predetermined value or more, shearing deformation can be caused to the clinch rubber. Good chaining performance can be obtained. Furthermore, in the rubber composition mainly composed of (III) natural rubber and silica, the wear resistance of the rubber itself is insufficient. Therefore, by setting the hardness of the clinch rubber to a certain value or more, better chafing performance can be obtained. can get. As described above, in the present invention, even if a part or all of raw materials derived from petroleum resources of clinch rubber are replaced with raw materials derived from non-petroleum resources according to the above (I) to (III), good chaining is achieved. Performance is obtained.

1 is a cross-sectional view illustrating a part of a pneumatic tire according to an embodiment of the present invention.

First, the rubber composition for clinch for producing the clinch rubber used for the pneumatic tire of this invention is demonstrated.

(Rubber composition for clinch)
The rubber composition for clinch is a total content of natural rubber, which is a raw material derived from non-petroleum resources, and a modified natural rubber, and a content of silica, which is a raw material derived from non-petroleum resources, in a reinforcing filler. Is greater than or equal to a predetermined amount. That is, the rubber composition for clinch is a rubber composition in which a part or all of raw materials derived from petroleum resources are replaced with raw materials derived from resources other than petroleum (the ratio of raw materials derived from petroleum resources is reduced). Therefore, by using the rubber composition, it is possible to prepare for the exhaustion of raw materials derived from petroleum resources and to consider the environment.

The total content of natural rubber (NR) and modified natural rubber in 100% by mass of the rubber component of the rubber composition for clinch is 70% by mass or more, preferably 85% by mass or more, and more preferably 100% by mass. If it is less than 70% by mass, the ratio of raw materials derived from petroleum resources cannot be sufficiently reduced, and the environment tends not to be considered sufficiently. NR includes deproteinized natural rubber (DPNR) and high-purity natural rubber (HPNR). Modified natural rubber includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafting. Examples include natural rubber. Moreover, as NR, what is common in tire industry, such as SIR20, RSS # 3, TSR20, can be used, for example.

In addition to NR and modified natural rubber, rubber components that can be used in the rubber composition for clinch include butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), isoprene rubber (IR), ethylene propylene. Examples include diene-based synthetic rubbers such as diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR). A diene type synthetic rubber may be used independently and may use 2 or more types together.

When the rubber composition for clinch contains a diene synthetic rubber, the content of the diene synthetic rubber in 100% by mass of the rubber component is 30% by mass or less. If it exceeds 30% by mass, the ratio of raw materials derived from petroleum resources cannot be sufficiently reduced, and the environment tends not to be considered sufficiently.

The rubber composition for clinch contains silica which is a raw material derived from resources other than petroleum. Silica functions as a reinforcing filler. By blending silica, the ratio of raw materials derived from petroleum resources can be reduced, and fuel efficiency and wear resistance can be improved.

The content of silica in 100% by mass of the reinforcing filler contained in the rubber composition for clinch is 50% by mass or more, preferably 70% by mass or more, more preferably 85% by mass or more, and further preferably 100% by mass. . If it is less than 50% by mass, the ratio of raw materials derived from petroleum resources cannot be sufficiently reduced, and there is a tendency that the environment cannot be fully considered.

Examples of the silica include, but are not limited to, dry method silica (anhydrous silicic acid), wet method silica (anhydrous silicic acid), and the like, and wet method silica is preferable because it has many silanol groups. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 50 m ² / g or more, more preferably 100 m ² / g or more. If it is less than 50 m < ² > / g, there exists a tendency for it to be inferior to abrasion resistance. Further, N ₂ SA of silica is preferably 300 m ² / g or less, more preferably 250 m ² / g or less, and further preferably 200 m ² / g or less. When it exceeds 300 m ² / g, the dispersibility tends to be inferior or the fuel efficiency tends to be inferior.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica in the rubber composition for clinch is preferably 30 parts by mass or more, more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 30 parts by mass, the wear resistance may not be sufficiently obtained. The content of the silica is preferably 100 parts by mass or less, more preferably 80 parts by mass or less. When it exceeds 100 parts by mass, the rubber viscosity becomes high, and the process passability (processability and productivity) tends to be inferior, or the fuel efficiency tends to deteriorate.

The rubber composition for clinching preferably contains a silane coupling agent together with silica. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry, and examples thereof include sulfide systems such as bis (3-triethoxysilylpropyl) disulfide, 3- Mercapto type such as mercaptopropyltrimethoxysilane, vinyl type such as vinyltriethoxysilane, amino type such as 3-aminopropyltriethoxysilane, glycidoxy type of γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxy Examples thereof include nitro compounds such as silane and chloro compounds such as 3-chloropropyltrimethoxysilane. Among these, sulfide type is preferable, and bis (3-triethoxysilylpropyl) tetrasulfide is more preferable.

The content of the silane coupling agent is preferably 4 parts by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 4 parts by mass, the rubber strength tends to decrease. Further, the content of the silane coupling agent is preferably 15 parts by mass or less, more preferably 12 parts by mass or less. When it exceeds 15 parts by mass, the wear resistance tends to be inferior.

Examples of the reinforcing filler include carbon black and calcium carbonate in addition to silica. For example, when carbon black is blended, the rubber reinforcement and wear resistance can be improved. However, from the viewpoint of resource saving and environmental protection, it is preferable that carbon black derived from petroleum / coal is not substantially contained (0% by mass).

In addition to the above components, the rubber composition for clinching includes compounding agents generally used in the production of rubber compositions, such as zinc oxide, stearic acid, various anti-aging agents, antioxidants, ozone deterioration inhibitors, oils And the like, vulcanizing agents such as wax and sulfur, vulcanization accelerators such as sulfenamide and guanidine, and the like can be appropriately blended.

The rubber composition for clinch is manufactured by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The hardness Hs of the clinch rubber (after vulcanization) is 75 or more, preferably 77 or more, more preferably 80 or more. If it is less than 75, the abrasion resistance of the clinch rubber itself is insufficient, and there is a possibility that sufficient chafing performance cannot be obtained. For example, by setting the silica content within the above range, the hardness Hs of the clinch rubber can be adjusted within the above range. In addition, in this specification, hardness is a value measured by the method as described in the below-mentioned Example.

The pneumatic tire of the present invention is produced by a normal method using the rubber composition for clinch. That is, by extruding the rubber composition for clinch blended with the above components in accordance with the shape of the clinch at an unvulcanized stage, and molding it with other tire members on a tire molding machine by a normal method. To form an unvulcanized tire. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a pneumatic tire.

In the present invention, even when a clinching rubber produced by using the clinching rubber composition obtained by substituting a part or all of a raw material derived from petroleum resources with a raw material derived from non-petroleum resources is used, By making the structure a specific structure, good chafing performance can be obtained.

Hereinafter, an example of a preferred embodiment of the pneumatic tire of the present invention will be described with reference to the drawings as appropriate.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. In FIG. 1, the vertical direction is the tire radial direction, and the horizontal direction is the axial direction.

As shown in FIG. 1, a pneumatic tire 1 includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a bead apex rubber 8 extending radially outward from the bead core 5. And a clinch rubber 9 disposed on the outer side in the tire axial direction of the bead apex rubber 8 and forming the outer surface of the bead portion 4. The tread portion 2 is provided with a tough belt layer 7 extending radially outward of the carcass 6 in the tire circumferential direction. An inner liner 15 forming a tire lumen surface is disposed on the radially inner side of the carcass 6.

The belt layer 7 is formed of two or more belt plies 7A and 7B in which high strength belt cords such as steel cords are arranged at an angle of, for example, 10 to 40 ° with respect to the tire circumferential direction. The belt cords cross each other between the plies, thereby increasing the belt rigidity, and substantially reinforcing the entire width of the tread portion 2 with a tagging effect. Further, on the outer side of the belt layer 7 in the radial direction, a band layer in which a band cord of an organic fiber such as nylon is spirally wound at an angle of 5 degrees or less with respect to the circumferential direction for the purpose of improving high-speed durability. 10 can be provided. As the band layer 10, a pair of left and right edge band plies that covers only the outer end portion of the belt layer 7 in the tire axial direction and a full band ply that covers substantially the entire width of the belt layer 7 can be used as appropriate. A band ply and a single full band ply may be used in combination.

Next, the carcass 6 is formed from two carcass plies 6A and 6B in the radial direction in which carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction. As the carcass cord, a well-known organic fiber cord such as nylon, polyester, rayon or the like is preferably used.

The inner carcass ply 6A includes a main body portion 11 straddling the bead cores 5 and 5 and a winding portion that is connected to the main body portion 11 and is wound around the bead core 5 from the inner side to the outer side in the tire axial direction. 12, and a hard bead apex rubber 8 extending radially outward from the bead core 5 is disposed between the main body 11 and the hoisting part 12.

The outer carcass ply 6B extends along the outer surface of the main body portion 11 of the inner carcass ply 6A, the main body portion 13 straddling the bead cores 5 and 5, and the main body portion 13 and the circumference of the bead core 5. It is formed as a so-called rolled-up carcass ply having a wound-up portion 14 that is wound up and locked from the inner side in the tire axial direction. The radially outer end of the winding part 14 is sandwiched between the winding part 12 of the carcass ply 6 </ b> A and the bead apex rubber 8 and is interrupted.

The bead apex rubber 8 includes an apex main portion 8A having a substantially triangular cross section extending radially outward from the bead core 5 and a substantially constant thickness extending radially outward from the apex main portion 8A. It is formed with a thin wing portion 8B extending at T. At this time, the thickness T is preferably in the range of 0 to 2 mm. When the wing portion 8B has a substantially constant thickness T and the thickness T is in the above range, the thickness of the clinch rubber (clinch rubber thickness 9M) can be increased.
Note that “substantially constant thickness T” allows ± 10% thickness variation due to a tire manufacturing process such as vulcanization molding and tapered thickness variation at the outer end. Is.

The apex main part height La, which is the radial height from the bead base line BL at the radially outer end of the apex main part 8A, is 25 mm or less, more preferably 23 mm or less, still more preferably 21 mm or less, particularly preferably 20 mm. Hereinafter, it is most preferably 17 mm or less. If it exceeds 25 mm, the thickness of the clinch rubber cannot be increased to a predetermined value or more, so that shear deformation cannot be caused to the clinch rubber, and sufficient chafing performance may not be obtained. The outer end in the radial direction of the apex main portion 8A exists at a position translated from the innermost position P of the clinch rubber 9 in the tire axial direction in the tire axial direction. That is, the radial height from the bead base line BL at the position P and the apex main portion height La are the same.

The apex height Lb in the radial direction from the bead base line BL at the radially outer end of the bead apex rubber 8 is preferably in the range of 10 to 40% of the tire cross-sectional height L (shown in FIG. 1). When it is in the above range, steering stability and durability (chafing performance) are good.

In this embodiment, the case where the bead apex rubber 8 is composed of the apex main portion 8A and the wing portion 8B has been described. However, the bead apex rubber of the present invention may be composed of only the apex main portion. .

In the present embodiment, the case where the wing portion 8B has a substantially constant thickness T has been described. However, in the present invention, the wing portion of the bead apex rubber may not have a substantially constant thickness. Good.

The clinch rubber 9 extends radially outward from the radial outer end of the chafer rubber 16 located at the radially inner end of the bead portion 4 and extends outward in the tire axial direction of the clinch rubber 9. A part of the side surface (outer surface S1) is exposed to form the outer surface of the bead portion 4. On the other hand, the inner surface S2 on the inner side in the tire axial direction of the clinch rubber 9 is in contact with the winding portion 12 of the carcass ply 6A.

Of the inner surface S2, an inner surface S2u (not shown) located radially outward from the radially outer end of the apex main portion (radial direction from the innermost position P in the tire axial direction of the clinch rubber 9) The clinch rubber thickness 9M, which is the minimum thickness from the outer side surface (outer side surface) to the outer side surface S1 (exposed outer surface of the outer surface of the clinch rubber in the tire axial direction) is 5.0 mm. The thickness is preferably 5.5 mm or more, more preferably 5.8 mm or more, and still more preferably 6.0 mm or more. If it is less than 5.0 mm, sufficient shear deformation cannot be caused in the clinch rubber, and sufficient chafing performance may not be obtained.

In addition, the winding part 12 which the said carcass ply 6A has is located between the said inner surface S2u and the said wing | blade part 8B. By adopting such a structure, steering stability is improved.

The clinch height Lc, which is the radial height from the bead base line BL at the radially outer end of the clinch rubber 9, is preferably in the range of 50 to 95% of the apex height Lb. When it is in the above range, steering stability and durability (chafing performance) are good.

As mentioned above, although an example of preferable embodiment of the pneumatic tire of this invention was demonstrated, this invention is not limited to the said embodiment, It can deform | transform and implement in a various aspect.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: SIR20
BR: BR150B manufactured by Ube Industries, Ltd.
Carbon black: Diamond Black I (N220) manufactured by Mitsubishi Chemical Corporation
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Silica: Ultrazil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Anti-aging agent: Antigen 6C (N- (1,3-dimethyl-butyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Zinc oxide: Zinc Hana No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. DPG: Noxeller D (diphenylguanidine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator TBBS: NOXERA-NS (TBBS) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-5 and Comparative Examples 1-6
(Preparation of rubber composition for clinch)
According to the blending contents shown in Table 1, using a 1.7 L Banbury mixer, among the blended materials, materials other than sulfur and a vulcanization accelerator were kneaded for 3 minutes at 150 ° C. to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the kneaded material obtained, and kneaded for 5 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. Furthermore, the obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 20 minutes to obtain a vulcanized rubber composition (clinch rubber).
(Production of test pneumatic tire)
The obtained unvulcanized rubber composition was extruded in accordance with the shape of the clinched portion, and bonded to other members to form an unvulcanized tire so as to have the basic structure shown in FIG. Vulcanization was carried out for 20 minutes under the condition of ° C. to produce a test pneumatic tire (size: 195 / 65R15 91H). The bead apex blade thickness T, apex main portion height La, Lb (radius apex height from the bead base line BL at the radially outer end of the bead apex rubber 8) / L (tire cross section height) The clinch rubber thickness of the clinch rubber is 9M and Lc (clinch height) / Lb is as shown in Table 1.

The following evaluation was performed using the obtained vulcanized rubber composition (clinch rubber) and a test pneumatic tire. Each test result is shown in Table 1.

(hardness)
Based on JIS K6253, the hardness of the obtained vulcanized rubber composition (clinch rubber) was measured using a hardness meter at a temperature of 25 ° C. (Shore-A measurement).

(Measurement of rim chaefing in durability test)
Using a test pneumatic tire, after performing a 30000 km drum running durability test under conditions of an internal pressure of 200 KPa, a load of 7 km, and a speed of 80 km / h, the tire was removed from the rim, and the thickness of the rim contact portion (clinch portion) Was compared with the thickness at the start of the test, and the amount of shaving (chafing amount) was measured. The smaller the amount of chafing, the better the chafing performance.

In the case of using a clinching rubber produced using a clinching rubber composition in which the total content of natural rubber and modified natural rubber is a specific amount or more, and the silica content in the reinforcing filler is a predetermined amount or more. Even if it exists, (i) Apex main part height La is below a specific value, (ii) Clinch rubber thickness 9M is made more than predetermined value, (iii) The hardness of clinch rubber is made more than a fixed value. The performance was good. Compared to Example 1, Example 2 having a small apex main portion height La and a large clinch rubber thickness 9M had better chafing performance than Example 1. Moreover, compared with Example 3, Example 2 in which the hardness of the clinch rubber was large was superior in chafing performance to Example 3. A large amount of butadiene rubber or carbon black, which is a petroleum resource-derived material (the total content of natural rubber and modified natural rubber is less than a specific amount, and / or the content of silica in the reinforcing filler is a predetermined amount. The following Comparative Examples 1 and 2 had good chafing performance even if the above (i) to (iii) were not satisfied. However, since petroleum resource-derived materials are used, it is impossible to prepare for the depletion of petroleum resource-derived raw materials or to consider the environment. Also, a clinching rubber produced using a clinching rubber composition in which the total content of natural rubber and modified natural rubber is a specific amount or more and the silica content in the reinforcing filler is a predetermined amount or more is used. Comparative Example 5 that does not satisfy (ii), Comparative Example 3 that does not satisfy (i) and (ii), Comparative Example 4 that does not satisfy (i) to (iii), and (iii) In Comparative Example 6 that was not satisfied, the chafing performance was inferior to that of the Example.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass ply 6B in carcass 6A Outside carcass ply 7 Belt layer 8 Bead apex rubber 8A Apex main part 8B Wing part 9 Clinch rubber 10 Band layer 11 Main part 12 Winding part 13 Body part 14 Winding part 15 Inner liner 16 Chafer

Claims (4)

A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, a bead apex rubber extending radially outward from the bead core, and an outer surface of the bead portion disposed on the outer side in the tire axial direction of the bead apex rubber A pneumatic tire having clinch rubber
The bead apex rubber has an apex main portion having a substantially triangular section extending radially outward from the bead core, and the apex main portion in the radial direction from the bead base line at the radially outer end of the apex main portion. The part height La is 25 mm or less,
Of the inner surface of the clinch rubber on the inner side in the tire axial direction, the inner surface of the clinch rubber on the outer side in the tire axial direction of the clinch rubber is exposed from the inner side surface located radially outward from the radial outer end of the apex main portion. The clinch rubber thickness which is the minimum thickness to the outer surface is 5.0 mm or more,
The hardness of the clinch rubber is 75 or more,
In the clinch rubber, the total content of natural rubber and modified natural rubber in 100% by mass of the rubber component is 70% by mass or more, and the content of silica in 100% by mass of the reinforcing filler is 50% by mass or more. A pneumatic tire manufactured using a rubber composition for clinch. The bead apex rubber is composed of the apex main part and a wing part that extends to the outer side in the radial direction and continues to the apex main part.
2. The pneumatic tire according to claim 1, wherein the carcass is positioned between an inner side surface of the clinch rubber positioned radially outward from a radially outer end of the apex main portion and the wing portion. The pneumatic tire according to claim 1 or 2, wherein the silica has a nitrogen adsorption specific surface area of 50 to 300 m ² / g. The pneumatic tire according to any one of claims 1 to 3, wherein in the rubber composition for clinching, the content of the silica is 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

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