JPH09277801A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which has superior appearance of a surface of a wing part and which has improved weatherability such as heat ozone proof, UV proof and durability. SOLUTION: A pneumatic tire has a wing part adjacent to a side wall part and the wing part is formed with rubber composition which contains ethylene/ propylene/dien rubber and halogenated butyl rubber. The content of ethylene/ propylene/dien rubber and the content of halogenated butyl rubber in the rubber composition are shown by formula: 20<=E+0.5X<=40 and formula: 10<=E<=30 when the total amount of rubber component in the rubber composition is 100 parts by weight and the content of halogenated butyl rubber is X parts by weight and iodine value of the ethylene/propylene/dien rubber is within 10-15 and ethylene/propylene ratio (weight ratio) of the ethylene/propylene/dien rubber is within 65/35-85/15.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic tire having excellent wing appearance, weather resistance, adhesiveness and durability.

[0002]

2. Description of the Related Art Conventionally, an antiaging agent has been compounded in a rubber composition used for forming a wing portion of a pneumatic tire in order to prevent deterioration due to ozone, ultraviolet rays and the like. However, when such an anti-aging agent is contained in the rubber composition of the wing, the anti-aging agent migrates to the surface of the wing of the pneumatic tire (bloom).
However, there is a problem in that the surface of the wing is discolored and the commercial value of the pneumatic tire is reduced. Further, if the compounding amount of the antioxidant is reduced in order to prevent the above-mentioned discoloration, cracks are likely to occur in the wing portion, and the durability of the pneumatic tire is deteriorated.

In order to solve such problems, the aging compounded in the rubber composition by increasing the ozone resistance and the ultraviolet resistance of the rubber component itself of the rubber composition in a specific portion of the pneumatic tire. Methods to reduce the amount of inhibitor are being investigated.

Examples of such methods include rubber blends containing ethylene propylene diene rubber with a reduced content of antioxidants or rubber blends containing halogenated butyl rubber with a reduced content of antioxidants. A method used for the wing part can be considered. However, according to these methods, the bending fatigue resistance of the wing portion is lowered and cracks are likely to occur.

Further, in JP-A-59-14502, the tire side portion extending from the upper portion of the bead portion to the lower portion of the shoulder portion through the sidewall portion has a two-layer inner and outer structure.
This outer surface layer is composed of a rubber composition composed of chlorinated butyl rubber, ethylene propylene diene rubber and diene rubber, and a pneumatic tire composed of a rubber composition whose main layer is in contact with the outer surface layer is mainly a diene rubber. It is disclosed. In JP-A-59-20708, a sheet is arranged in the tire circumferential direction so as to cover the tire surface from the shoulder portion to the sidewall portion, and the sheet is made of natural rubber, polybutadiene rubber, halogenated butyl rubber and / or ethylene. A pneumatic tire composed of a rubber compound composed of propylene diene rubber is disclosed.
Further, JP-A-1-297307 discloses a two-layer structure in which a sidewall has an inner layer adjacent to a carcass and an outer layer disposed outside the carcass, and the inner layer comprises a halogenated butyl rubber and an ethylene propylene diene rubber. A rubber composition comprising at least one type of saturated rubber group and at least one type of highly unsaturated rubber group consisting of natural rubber, isoprene rubber, butadiene rubber and styrene-butadiene rubber, wherein the outer layer has the above-mentioned low content. A pneumatic tire composed of at least one kind of unsaturation rubber group and at least one kind of the high unsaturation rubber group is disclosed. However, these publications do not teach the polymer structure of the ethylene propylene diene rubber used.

Further, Japanese Patent Laid-Open No. 4-43106 discloses that
The outermost layer of the sidewall portion composed of a plurality of layers is composed of a rubber composition having a high iodine value and a high ethylene content of ethylene propylene diene rubber in an amount of 15% by weight or more of the rubber component and a reduced content of the antioxidant. A pneumatic tire is disclosed. However, according to a pneumatic tire using a rubber composition of this publication having a high iodine value and a high ethylene content ethylene propylene diene rubber in the sidewall portion, the sidewall portion is apt to cause poor adhesion, In addition, minute cracks are likely to exist in the sidewall portion. Therefore, when such a pneumatic tire is subjected to a drum durability test under severe conditions, for example, interlayer adhesion failure of the sidewall portion or cracking of the sidewall portion is likely to occur.

That is, the rubber composition for the wing portion of the pneumatic tire of the present invention cannot be designed based on the knowledge of the rubber composition for the sidewall portion described in these publications.

[0008]

SUMMARY OF THE INVENTION The present invention improves a rubber composition forming a wing portion of a pneumatic tire having a wing portion adjacent to a sidewall portion, thereby improving the appearance, weather resistance, and durability of the wing portion. It is intended to improve interlayer adhesion and durability. Another object of the present invention is to further improve the appearance of the wing portion by further improving the rubber composition forming the sidewall portion of the pneumatic tire.

[0009]

SUMMARY OF THE INVENTION The present invention has a wing adjacent to a sidewall portion, the wing including an ethylene propylene diene rubber (hereinafter sometimes referred to as "EPDM") and a halogenated butyl rubber (hereinafter, " X-II
R))), the total amount of rubber components in the rubber composition is 100 parts by weight, the EPDM content is E parts by weight, and X-II
When the content of R is X parts by weight, the content of EPDM and the content of X-IIR in the rubber composition are represented by the formula: 20 ≦ E + 0.5X ≦ 40 and the formula: 10 ≦ E ≦ 30. The pneumatic tire has the iodine value of EPDM in the range of 10 to 15 and the ethylene / propylene ratio (weight ratio) of the EPDM in the range of 65/35 to 85/15.

Further, in the present invention, the sidewall portion is composed of a rubber composition containing EPDM and X-IIR, and the total amount of the rubber component in the rubber composition is 100 parts by weight, and the content of EPDM is As E parts by weight, X-IIR
When the content of X is X parts by weight, E in the rubber composition is
The content of PDM and the content of X-IIR are represented by the formula: 25 ≦ E + 0.5X ≦ 35 and the formula: 15 ≦ E ≦ 25, and the iodine value of the EPDM is in the range of 10 to 15. , A pneumatic tire in which the ethylene / propylene ratio (weight ratio) of the EPDM is within the range of 65/35 to 85/15.

Further, in the present invention, the sidewall portion is composed of a plurality of layers, and the outermost layer of the plurality of layers is an EP.
It is composed of a rubber composition containing DM and X-IIR, the total amount of rubber components in the rubber composition is 100 parts by weight, the content of EPDM is E parts by weight, and the content of X-IIR is X. When the amount is parts by weight, EPD in the rubber composition
The content of M and the content of X-IIR are represented by the formula: 25 ≦ E + 0.5X ≦ 35 and the formula: 15 ≦ E ≦ 25, and the iodine value of the EPDM is in the range of 10 to 15. , A pneumatic tire in which the ethylene / propylene ratio (weight ratio) of the EPDM is within the range of 65/35 to 85/15.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The pneumatic tire of the present invention has a sidewall portion for covering and protecting the side surface of a carcass, and a wing portion adjacent to the sidewall portion. Further, since the wing portion is formed of a specific rubber composition that does not require an antioxidant, the pneumatic tire of the present invention is excellent in appearance, weather resistance, interlayer adhesion and durability of the wing portion. It has characteristics.

Further, according to the present invention, by further forming the entire sidewall portion or the outermost layer portion with a specific rubber composition containing no antiaging agent, the appearance and weather resistance of the wing portion are further improved. It is possible to obtain a pneumatic tire.

The rubber component of the rubber composition forming the wing contains a specific amount of EPDM, and X
-IIR is contained in a specific amount. By using such a rubber component, it is possible to obtain a wing portion rubber composition having excellent weather resistance without using an antioxidant.
Further, by using such a rubber composition in the wing portion, it is possible to suppress the generation of microcracks in the wing portion, and the adhesion between the wing portion and the portion in contact with the wing portion is improved, so that the pneumatic tire Will have excellent durability.

When the total amount of the rubber component in the rubber composition of the wing part is 100 parts by weight, the specific EPDM content is E parts by weight, and the X-IIR content is X parts by weight, The EPDM content and the X-IIR content of are within the range represented by the formula: 20 ≦ E + 0.5X ≦ 40 and the formula: 10 ≦ E ≦ 30. The value of E + 0.5X is 2
If it is less than 0, the weather resistance such as ozone resistance and ultraviolet resistance of the wing becomes poor. Further, when the value of E is less than 10, weather resistance such as ozone resistance and ultraviolet resistance of the wing becomes poor. E + 0.5X
If the value of exceeds 40, the adhesiveness between the wing portion and the sidewall portion is deteriorated. Further, when the value of E exceeds 30, the adhesiveness between the wing portion and the sidewall portion deteriorates.

The content of the specific EPDM in the rubber component in the rubber composition of the wing and X-II.
The content of R is preferably represented by the formula: 22.5 ≦ E + 0.5X ≦ 37.5 and the formula: 12 ≦ E ≦ 28.

If the value of E + 0.5X is smaller than 22.5, the weather resistance may be slightly deteriorated. On the other hand, 3
If it is larger than 7.5, the adhesiveness between the wing portion and the sidewall portion may be slightly deteriorated. Also,
If the value of E is less than 12, the weather resistance may be slightly deteriorated. On the other hand, if it is greater than 28, the adhesion between the wing portion and the sidewall portion may be slightly deteriorated.

When the value of E + 0.5X and the value of E are within the range represented by the above formula, good weather resistance such as ozone resistance and ultraviolet resistance is obtained without adding an antiaging agent, and adhesion is excellent. A good rubber composition for the wing can be obtained. Also, as mentioned above, a suitable amount of X-II
By blending R, EPDM easily disperses in the rubber composition, and for this reason, weather resistance such as ozone resistance and ultraviolet resistance of the wing part using this rubber composition is improved, and It is considered that no microcracks can be seen in the wing parts.

The iodine value of the specific EPDM is 1
It is in the range of 0 to 15. If the iodine value of the specific EPDM is less than 10, the adhesiveness between the wing portion and the portion in contact with the wing portion becomes poor. On the other hand, if it is greater than 15, fine cracks are likely to occur in the wing portion. In addition, EPDM with an iodine value greater than 15
Is also disadvantageous in that it is expensive.

The ethylene / propylene ratio (weight ratio) of the specific EPDM is in the range of 65/35 to 85/15, preferably in the range of 70/30 to 82.5 / 17.5. If the weight of ethylene of the particular EPDM is less than the range above with respect to the weight of propylene,
If the adhesion between the wing and the part in contact with the wing becomes poor, on the other hand, if it exceeds the above range, EPDM
Has a tendency to become highly crystalline and less likely to exhibit rubber elasticity, which is not preferable.

Examples of the X-IIR include butyl chloride rubber, brominated butyl rubber, etc. Among them, chlorinated butyl rubber (hereinafter referred to as "Cl-IIR") has good compatibility with diene rubber. Sometimes
It is preferable to use

In addition to the specific EPDM and X-IIR, the rubber composition forming the wing portion contains a diene rubber as a rubber component. As the diene rubber, any of those generally used as a rubber component for the wing portion can be used, and for example, one kind or two or more kinds of natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber and the like can be used. Can be used.

A rubber composition for a wing portion can be obtained by blending these rubber components with a conventional compounding agent excluding an antioxidant. Examples of compounding agents to be added to the rubber composition include carbon black; process oils; mastication accelerators such as zinc white, mercaptans, and disulfides; vulcanization accelerators such as stearic acid and zinc white; sulfur, insolubility Vulcanizing agents such as sulfur; sulfenamide-based and thiazole-based vulcanization accelerators and the like are included, and an appropriate amount thereof is blended according to required quality.

A pneumatic tire having a wing portion formed of such a rubber composition has an excellent appearance of the wing portion, good weather resistance and excellent durability.

The wing portion is adjacent to the sidewall portion. Therefore, if the sidewall portion contains the antioxidant, the antioxidant contained in the sidewall portion may migrate to the wing portion and bloom on the surface of the wing portion. Further, when the side wall portion is formed of a rubber composition having a composition requiring an anti-aging agent, if the anti-aging agent migrates to the wing portion, the side wall portion may be partially lacking in the anti-aging agent. In such a case, the weather resistance of the part where the antioxidant is insufficient becomes poor.

In order to prevent such a phenomenon, the rubber composition forming the sidewall portion is made to have a specific EPD.
It is preferable that the composition contains M in a specific amount and X-IIR in a specific amount and does not contain an antioxidant. By using such a rubber composition part in the side wall part, it is possible to prevent migration of the anti-aging agent to the wing part as described above, and it is possible to suppress generation of minute cracks in the side wall part due to use of EPDM. .

When the total amount of the rubber component in the rubber composition of the sidewall portion is 100 parts by weight, the specific EPDM content is E parts by weight, and the X-IIR content is X parts by weight, Specific EPDM content and X-IIR
Within the range represented by the formula: 25 ≦ E + 0.5X ≦ 35 and the formula: 15 ≦ E ≦ 25, in particular, 27.5 ≦ E + 0.5X ≦ 35 and the formula: 17 ≦ E ≦ 25. It is preferably within the range represented. E +
If the value of 0.5X is smaller than 25, the weather resistance such as ozone resistance and ultraviolet resistance of the side wall part tends to be poor, while if it is larger than 35, the side wall part and the wing part are Or the adhesiveness between the sidewall portion and the portion in contact with the sidewall portion tends to be poor. Further, when the value of E is less than 15, the weather resistance such as ozone resistance and ultraviolet resistance of the sidewall portion tends to be poor, while when it is more than 25, the sidewall portion and the wing portion tend to be deteriorated. The adhesiveness between the side wall portion and the portion in contact with the side wall portion tends to be poor.

When the value of E + 0.5X and the value of E are within the range represented by the above formula, good weather resistance such as ozone resistance and ultraviolet resistance can be obtained without adding an anti-aging agent, and adhesion can be improved. A good rubber composition for a sidewall can be obtained.

Also, such specific EPDM and X
Examples of -IIR include the same as the specific EPDM and X-IIR used for the wing part.
Further, as the compounding agent used for the rubber composition for the side wall part, the same compounding agent as used for the wing part may be mentioned.

Further, in order to prevent migration of the antioxidant from the side wall portion to the wing portion, the side wall portion is formed of a plurality of layers, and only the outermost layer of the plurality of layers is used for the side wall portion. A rubber composition similar to the rubber composition may be used, and the inner layer thereof may be formed of a conventionally known rubber composition for a sidewall portion (however, containing no antioxidant). The inner layer may be composed of one layer or two or more layers composed of different rubber compositions. Examples of the rubber component of the inner layer rubber composition include one or more diene rubbers such as natural rubber, isoprene rubber, styrene-butadiene rubber, and butadiene rubber. Examples of compounding agents to be added to such rubber compositions include carbon black; process oils; mastication accelerators such as zinc white, mercaptans, and disulfides; vulcanization accelerators such as stearic acid and zinc white. Vulcanizing agents such as sulfur and insoluble sulfur;
Examples include vulcanization accelerators such as sulfenamide type and thiazole type. In the rubber composition of the inner layer of the sidewall portion, the specific EPDM, other EPDM or X-IIR may be blended in an appropriate amount in order to improve adhesion with the outer layer of the sidewall portion. But,
In that case, the cost tends to increase. In addition,
In this way, the sidewall portion has a multi-layer structure, and by not incorporating an antioxidant into the rubber composition of the inner layer,
The antioxidant migrates from the inner layer of the sidewall part to the wing part through the outermost layer, or from the case part to the wing part through the inner layer and outermost layer of the sidewall part and blooms on the wing surface. Can be prevented.

The thickness of the outermost layer of the sidewall portion is
Since the cost increases as the thickness increases, and the reinforcing property decreases as the thickness decreases, the thickness is preferably within the range of 0.4 to 0.8 mm. The thickness of the inner layer of the sidewall (when the inner layer is composed of two or more layers, the total thickness thereof)
Is thicker, the rolling resistance is higher and the cost is higher.
It is preferable that it is within the range of about 2.5 to 3.5 mm.

[0032]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

As the rubber and compounding agent of the rubber composition for the wing portion and the rubber composition for the sidewall portion of the following Examples and Comparative Examples, EPDM: ethylidene norbornene as shown in Table 1 was used as the diene component. 4 types (E for each type
They were PDM, EPDM, EPDM and EPDM. EPDM and EPDM are EPDs according to the present invention
M), Cl-IIR: Cl-IIR manufactured by Exxon Chemical Co., Ltd.
HT1066, Natural rubber: RSS1, Butadiene rubber: BR130B made by Ube Industries, Carbon black: N550 made by Tokai Carbon Co., Process oil: Diana Process PS32 made by Idemitsu Kosan, Wax: Shin Ouchi Sannox wax manufactured by Kagaku Co., Ltd., anti-aging agent: Ozonone 6C manufactured by Seiko Chemical Co., Ltd., Zinc flower: Zinc flower No. 1 manufactured by Sakai Chemical Industry Co., Ltd., Stearic acid: manufactured by NOF CORPORATION. Paulownia stearate, sulfur: Sulfur manufactured by Tsurumi Chemical Co., Ltd., and vulcanization accelerator: Nocceller NS manufactured by Ouchi Shinko Chemical Co., Ltd. were used.

[0034]

[Table 1]

Examples 1 and 2 and Comparative Examples 1 to 6 The amounts of the rubber component and the compounding agent component of the wing rubber composition shown in Table 2 shown in Table 2 were kneaded by a conventional method,
By extruding, an unvulcanized rubber sheet for the wing portion was obtained.

45 parts by weight of natural rubber, 55 parts by weight of butadiene rubber, 60 parts by weight of carbon black, 8 parts by weight of process oil, 1.5 parts by weight of wax, 2.5 parts by weight of antioxidant, 2 parts by weight of zinc oxide. Then, 3 parts by weight of stearic acid, 1.5 parts by weight of sulfur and 1 part by weight of a vulcanization accelerator were kneaded by a usual method and extruded to prepare an unvulcanized rubber sheet for the sidewall part.

Using the unvulcanized rubber sheet for the wing portion and the sidewall portion, the wing portion and the sidewall portion are formed, and the structure shown in FIG. 185 / 70R14
The pneumatic tire of was produced.

<Evaluation of Pneumatic Tire><Evaluation of Ozone in Pneumatic Tire> The above pneumatic tire was assembled into a rim (air pressure 2.0 kgf / cm ² ), and the temperature was set to 4.
It was placed in an ozone chamber at 0 ° C. and an ozone concentration of 50 PPhm, and the discoloration (appearance) of the wing part and the state of generation of cracks were observed every day for 7 days by the following method. The results are shown in Table 2.

(Evaluation of appearance of wing portion) The wing portion is visually observed and judged according to the following criteria. A: No discoloration was observed after 7 days. B: Some discoloration was observed after 7 days. C ... Discoloration was observed after 7 days. D: Discoloration is considerably observed after 7 days.

It can be said that the case where the judgment is "A" or "B" is in the practical range.

(Evaluation of Wing Crack) The wing is visually observed and judged according to the following criteria. Good: No cracks were observed after 7 days. 6 ... A crack occurred on the 6th day. 7: Cracks occurred on the 7th day.

It can be said that the case where the judgment is “◯” is in the practical range.

<Drum Durability Test (I)> Using this pneumatic tire, a durability performance test was conducted in accordance with the conditions specified in JIS D4230. After the durability test, the interlayer adhesion between the wing portion and the sidewall portion of the pneumatic tire was evaluated and the presence of microcracks in the outer layer was observed as follows. The results are shown in Table 2.

(Interlayer adhesion between wing portion and sidewall portion) After the drum durability test, the wing portion and the sidewall portion are cut into strips each having a width of 1 cm so that a peeling test between the wing portion and the sidewall portion can be performed. To
Make a notch between the wing and sidewall with a cutter. Then, the notched portion of the wing portion and the notched portion of the sidewall portion are respectively sandwiched by chucks and pulled at a chuck-to-chuck speed of 10 mm / min to perform a peeling test between the wing portion and the sidewall portion. And the side wall portion were evaluated for interlayer adhesiveness (hereinafter, also referred to as adhesiveness (between wing and SW)). When the wing part was cut out together with the sidewall part and there was already a part where interface delamination was present between the wing part and the sidewall part, it was designated as "x", and what was interfacially destroyed by the delamination test was designated as "x". The result of cohesive failure in the peeling test is judged as "○".

It can be said that the case where the judgment is “◯” is in the practical range.

(Observation of State of Presence of Microcracks in Wing) After the drum durability test, the microcracks in the wing are visually observed.

The case where no microcracks were observed was judged as "◯", the case where a small amount of microcracks was observed was judged as "Δ", and the case where a large number of microcracks were observed was judged as "x".

It can be said that the case where the judgment is “◯” is in the practical range.

<Drum durability test (II)> JIS D42
A durability test of a pneumatic tire was conducted in the same manner as the drum durability test (I) except that the load condition specified in No. 30 was doubled, and interlayer adhesion between the wing portion and the sidewall portion was performed by the same method. The property was evaluated and the presence of microcracks in the wing was observed. The results are shown in Table 2. The criteria and method of determination are the same as in the drum durability test (I).

Comparative Example 7 Aside from substituting the rubber composition for the wing part with the rubber composition for the wing part (conventional rubber composition for the sidewall part containing an antioxidant and a wax) shown in Table 2, Comparative Example 7 was carried out. A pneumatic tire having the same structure as in Example 1 was produced in the same manner as in Example 1, and the same evaluation as in Example 1 was performed using this pneumatic tire. The results are shown in Table 2.

[0051]

[Table 2]

Examples 3 to 12 and Comparative Examples 8 to 11 A wing rubber composition (in the same manner as in Example 1 except that the rubber composition of the rubber composition for the wing portion was changed to the composition shown in Table 3). The compounding agent components were the same as in Example 1), and a pneumatic tire having the same structure as in Example 1 was prepared. Using this pneumatic tire, ozone evaluation of the pneumatic tire was performed in the same manner as in Example 1. Table 3 shows the results.

A drum durability test (II) of the pneumatic tire was conducted in the same manner as in Example 1 using the same pneumatic tire. In addition, in the drum durability test (II) in this example and the comparative example, evaluation of adhesion (between wing / SW) by the same method as in Example 1 and wing portion by the same method as in Example 1 In addition to the evaluation of minute cracks, the following minute cracks in the sidewall portion were evaluated. Table 3 shows the results.

(Observation of Presence of Minute Cracks on Sidewall) After the drum durability test, the minute cracks on the sidewall are visually observed.

The case where no minute cracks were observed was judged as “◯”, the case where a small amount of minute cracks was observed was judged as “Δ”, and the case where a large number of minute cracks were observed was judged as “x”.

It can be said that the case where the judgment is “◯” is in the practical range.

In Table 3, the composition of the rubber composition of Example 2 already described in Table 2 and the evaluation results are also shown.

[0058]

[Table 3]

Examples 13 to 27 Table 4 of the rubber component and compounding agent component shown in Table 4 or 5
Alternatively, an unvulcanized rubber sheet of a rubber composition for a side wall portion was prepared by kneading and extruding the amount described in 5 by a usual method and using this as a rubber composition for a side wall. A pneumatic tire having the same structure was produced in the same manner as in (the rubber composition for the wing portion was the same as in Example 2).

Using this pneumatic tire, ozone evaluation of the pneumatic tire was carried out in the same manner as in Example 1.
The results are shown in Tables 4 and 5.

A drum durability test (II) of the pneumatic tire was carried out in the same manner as in Example 1 using the same pneumatic tire. Also in the drum durability test (II) in this example, the adhesiveness (between wing and SW) was evaluated by the same method as in Example 1 and small cracks in the wing portion were evaluated by the same method as in Example 1. Besides evaluation,
The same method as in Example 3 was used to evaluate the minute cracks in the sidewall portion. Further, in this example, the interlayer adhesion between the case portion and the sidewall portion shown below was evaluated. The results are shown in Tables 4 and 5.

(Interlayer Adhesion Between Case and Sidewall) After the drum durability test, the case and the sidewall are cut into strips each having a width of 1 cm so that a peeling test between the case and the sidewall can be performed. Then, make a notch with a cutter between the case and the sidewall. Then, the notched portion of the case portion and the notched portion of the sidewall portion are respectively sandwiched by chucks and pulled at a chuck-to-chuck speed of 10 mm / min to perform a peeling test between the case portion and the sidewall portion.
The interlayer adhesiveness between the case portion and the sidewall portion (hereinafter, also referred to as adhesiveness (between case / SW)) is evaluated. When the case part was cut out together with the side wall part and there was already a part where the interface was peeled between the case part and the side wall part, it was designated as “x”, and the one which was interface-fractured by the peeling test was designated as “x”. The result of cohesive failure in the peeling test is judged as "○".

It can be said that the case where the judgment is “◯” or “Δ” is in the practical range.

[0064]

[Table 4]

[0065]

[Table 5]

Examples 28 to 41 The sidewall portion has a two-layer structure, the outer layer is formed of the rubber composition for the outer layer of the sidewall portion shown in Table 6, and the inner layer is 45 parts by weight of natural rubber and 55 parts by weight of butadiene. , Carbon black 60 parts by weight, process oil 8 parts by weight,
2 parts by weight of zinc white, 3 parts by weight of stearic acid, 1.5 parts by weight of sulfur and 1 part by weight of vulcanization accelerator are kneaded by a usual method,
As in Example 1 (the rubber composition for the wing portion is the same as that in Example 2) except that the rubber composition for the inner layer of the sidewall portion obtained by extrusion is formed, a schematic partial cross-sectional view is shown in FIG. A 185 / 70R14 pneumatic tire having a structure was produced. The gauge of the outer layer of the sidewall portion of this pneumatic tire was 0.6 mm on average, and the gauge of the inner layer was 2.4 mm on average.

Using this pneumatic tire, ozone evaluation of the pneumatic tire was carried out in the same manner as in Example 1.
Table 6 shows the results.

Using this pneumatic tire, the drum durability test (II) of the pneumatic tire was conducted in the same manner as in Example 1. Also in this example, in addition to the evaluation of the adhesiveness (between wing and SW) by the same method as in Example 1 and the evaluation of the minute cracks in the wing portion by the same method as in Example 1, as in Example 3. The same method was used to evaluate minute cracks in the sidewall portion and the same method as in Example 13 was evaluated for adhesiveness (between case and SW). Further, in this example, the interlayer adhesion between the inner layer of the side wall portion and the outer layer of the side wall portion was evaluated as follows. Table 6 shows the results.

(Interlayer Adhesion between Inner Layer of Sidewall Part and Outer Layer of Sidewall Part) After a drum durability test, the inner layer of the side wall part was cut out together with the outer layer of the side wall part into strips each having a width of 1 cm. A cut is made between the inner layer of the sidewall portion and the outer layer of the sidewall portion with a cutter so that a peeling test between the inner layer of the sidewall portion and the outer layer of the sidewall portion can be performed. Then, the notch of the inner layer of the sidewall portion is sandwiched between the notch of the outer layer of the sidewall portion by a chuck, and the chuck is pulled at a chucking speed of 10 mm / min, whereby the outer layer of the sidewall portion and the inner layer of the sidewall portion are separated from each other. By performing a peeling test, the interlayer adhesion between the inner layer of the sidewall portion and the outer layer of the sidewall portion (hereinafter, also referred to as adhesiveness (SW inner layer / SW outer layer) may be evaluated). When the inner layer of the side wall part is cut out together with the outer layer of the side wall part, there is already a part where the interface is separated between the inner layer of the side wall part and the outer layer of the side wall part. What is peeled off at the interface by the peeling test is judged as “Δ”, and what is cohesively destroyed by the peeling test is judged as “◯”.

It can be said that the case where the judgment is “◯” or “Δ” is in the practical range.

[0071]

[Table 6]

[0072]

EFFECTS OF THE INVENTION According to the present invention, good weather resistance such as ozone resistance and ultraviolet resistance is obtained without adding an antioxidant.
It is possible to obtain a wing rubber compound having good adhesion. By using a specific rubber compound that does not contain such an anti-aging agent in the wing part, the appearance of the wing part surface is excellent, there are no microcracks in the wing part, and weather resistance such as ozone resistance and ultraviolet resistance is high. It is possible to obtain a pneumatic tire having excellent durability and durability.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view of pneumatic tires according to Examples 1-27 and Comparative Examples 1-11.

FIG. 2 is a schematic partial cross-sectional view of pneumatic tires according to Examples 28 to 41.

[Explanation of symbols]

 1 Case (Carcass) Part 2 Wing Part 3 Sidewall Part 4 Case (Carcass) Part 5 Wing Part 6 Outer Layer of Sidewall Part 7 Inner Layer of Sidewall Part 8 Sidewall Part

Claims (3)

[Claims] 1. A rubber composition having a wing portion adjacent to a side wall portion, the wing portion comprising a ethylene propylene diene rubber and a halogenated butyl rubber, and the total amount of the rubber component in the rubber composition. Is 100 parts by weight, and the content of ethylene propylene diene rubber is E
When the content of the halogenated butyl rubber is X parts by weight, the content of the ethylene propylene diene rubber and the content of the halogenated butyl rubber in the rubber composition are represented by the formula: 20 ≦ E + 0.5X ≦ 40. The formula: 10 ≦ E ≦ 30, the ethylene propylene diene rubber has an iodine value within the range of 10 to 15, and the ethylene propylene diene rubber has an ethylene / propylene ratio (weight ratio) of 65.
A pneumatic tire in the range of / 35 to 85/15. 2. The side wall portion is composed of a rubber composition containing ethylene propylene diene rubber and halogenated butyl rubber, and the total amount of the rubber component in the rubber composition is 100 parts by weight. When the content is E parts by weight and the halogenated butyl rubber content is X parts by weight, the ethylene propylene diene rubber content and the halogenated butyl rubber content in the rubber composition are calculated by the formula: 25 ≦ E + 0. 5X ≦ 35 and the formula: 15 ≦ E ≦ 25, the ethylene propylene diene rubber has an iodine value in the range of 10 to 15, and the ethylene / propylene ratio (weight ratio) of the ethylene propylene diene rubber. Is 65
The pneumatic tire according to claim 1, which is in a range of / 35 to 85/15. 3. The sidewall portion is composed of a plurality of layers, and the outermost layer of the plurality of layers is composed of a rubber composition containing ethylene propylene diene rubber and halogenated butyl rubber. When the total amount of the rubber component is 100 parts by weight, the content of the ethylene propylene diene rubber is E parts by weight, and the content of the halogenated butyl rubber is X parts by weight, the ethylene propylene diene rubber in the rubber composition is The content and the content of the halogenated butyl rubber are represented by the formula: 25 ≦ E + 0.5X ≦ 35 and the formula: 15 ≦ E ≦ 25, and the iodine value of the ethylene propylene diene rubber is within the range of 10 to 15. And the ethylene / propylene ratio (weight ratio) of the ethylene propylene diene rubber is 65
The pneumatic tire according to claim 1, which is in a range of / 35 to 85/15.