JPH01297307A - Pneumatic tyre - Google Patents

Abstract

PURPOSE:To improve the durability and/or the adhesiveness and prevent the discoloration of a pneumatic tyre by forming each of inner and outer layers which form a sidewall, out of each of rubber constructions which has each one or more kind of rubber incorporated therewith at a specific rate of the low-unsaturated rubber group and each one or more kind of rubber incorporated therewith at a different specific rate of the high-unsaturated rubber group. CONSTITUTION:A sidewall 2 which protectingly covers the side face of a carcass 1 is formed of its inner layer 3 and its outer layer 4. In this case, the inner layer 3 is formed of rubber composition having one or more kinds of low-unsaturated rubber incorporated therewith by 10-30 weight portion among the rubber group of low degree of unsaturation consisting of butyl rubber halide and ethylene-propylene-diene rubber, and having one or more kinds of high-unsaturated rubber incorporated therewith by 90-70 weight portion among the rubber group of high degree of unsaturation consisting of natural rubber, isoprene rubber, butadiene rubber and styrene-butadiene rubber; while the outer layer 4 is formed of rubber composition having one or more kinds of rubber among the low unsaturated rubber group incorporated therewith by 30-60 weight portion, and having one or more kinds of rubber among the high- unsaturated rubber group incorporated therewith by 70-40 weight portion.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a pneumatic tire, and more specifically to a pneumatic tire in which a sidewall that covers and protects the side surface of a carcass is composed of two layers, an inner and outer layer having different rubber compositions. Regarding.

[Prior art] Sidewalls of pneumatic tires are made of natural rubber with a high content of double bonds in the main chain, isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (
It was made of a highly unsaturated rubber composition such as SBR). The double bonds in the main chain of this rubber molecule have the property of reacting with ozone and depolymerizing, so do not place the tire in a place with strong ultraviolet rays.
Alternatively, if it is left in an atmosphere with a high ozone concentration in the air, a so-called ozone crack will occur. To prevent this, sidewall rubber compositions have been blended with anti-ozone cracking agents such as amine anti-aging agents and wax.

However, in pneumatic tires that have sidewalls made of rubber compositions containing such anti-ozone cracking agents, the anti-ozone cracking agents bloom on the surface of the sidewalls during storage, causing dust to adhere to the tires. exhibits the appearance of Furthermore, amine anti-aging agents have the property of turning brown when exposed to air or sunlight, so the thin layer of anti-ozone cracking agent formed on the surface of the sidewall due to bloom turns brown, causing the tire to deteriorate. The original black color was hidden, spoiling the aesthetic appearance and lowering the product value.

Therefore, we use a low-unsaturation rubber with a low content of unsaturated bonds to increase the ozone resistance of the rubber component itself, and use a rubber composition with a reduced content of anti-ozone agents that cause blooming and discoloration. Consideration was made to construct a wall (for example, Japanese Patent Application Laid-Open No. 55-80448, Japanese Patent Application Laid-open No. 59-14502).
No., JP-A-82-143955).

[Problems to be Solved by the Invention] However, low unsaturation rubbers have slower vulcanization reactivity than diene rubbers (high unsaturation rubbers) commonly used for carcass and treads. Therefore, even if the vulcanization accelerator is adjusted to match the vulcanization rate of both, the vulcanization rate will locally increase due to migration of the vulcanization accelerator at the interface between the two, and the two rubbers will diffuse into each other. Since the period is short, the adhesion is poor. To solve this problem, as shown in Japanese Patent Application Laid-Open No. 59-14502, the sidewall has a two-layer structure, an inner and outer layer, and the outer layer is made of a rubber composition containing a large amount of low-unsaturation rubber.
Composing the inner layer with diene rubber did not solve the problem, and pneumatic tires using low-unsaturation rubber for the sidewalls had not been put into practical use.

The present invention solves the above problems and provides a pneumatic tire that uses a low unsaturation rubber and has a sidewall that is made of a diene rubber composition and has excellent adhesion to a carcass or the like. The purpose is

[Means for Solving the Problems] The pneumatic tire of the present invention has a sidewall (2) that covers and protects the side surface of the carcass (1), which is disposed on the inner layer (3) adjacent to the carcass and on the outside thereof. A pneumatic tire having a two-layer structure including an outer layer (4), wherein the inner layer (3) contains at least one member of the low unsaturation rubber group consisting of halogenated butyl rubber and ethylene propylene Φ diene rubber (EPDM). 30 parts by weight, and at least one member of the highly unsaturated rubber group consisting of natural rubber, isoprene rubber, butadiene rubber, and styrene-butadiene rubber.
The outer layer (
4) contains at least one member of the low unsaturation rubber group at 30%
60 parts by weight, and 70 to 40 parts by weight of at least one of the aforementioned highly unsaturated rubbers.

In addition, the inner layer (3) contains 10 to 30 parts by weight of brominated butyl rubber, 0 to 20 parts by weight of ethylene propylene diene rubber, and 9 parts by weight of at least one of the highly unsaturated rubber group.
The outer layer (4) is composed of a rubber composition containing 0 to 70 parts by weight of brominated butyl rubber, 20 to 60 parts by weight of brominated butyl rubber, 10 to 30 parts by weight of ethylene propylene diene rubber,
and at least one member of the group of highly unsaturated rubbers of 70 to 4
It is preferable to use a rubber composition containing 0 parts by weight.

In addition, the sidewall (2) that covers and protects the side surface of the carcass (1) with a radial structure has a two-layer structure consisting of an inner layer (3) adjacent to the carcass (1) and an outer layer (4) disposed outside of the inner layer (3). The upper end (6) of the sidewall is disposed on the side of the tread rubber (8) and extends while gradually decreasing in thickness until it ends, and the lower end (7) of the sidewall is disposed on the side of the tread rubber (8). The lower end (7) of this sidewall is followed by a rim strip (9) of decreasing thickness, terminating at the lower end (7) of the sidewall (2), at the upper end (6) of the sidewall (2), and at the main part (5).
) and the lower end portion (7), each of which contains 10 to 30 parts by weight of at least one of the low unsaturation rubber group and 90 to 70 parts by weight of at least one of the high unsaturation rubber group. Comprised of a rubber composition, the sidewall (2)
The outer layer of each of the upper end part (6), main part (5) and lower end part 7) contains 30 to 60 parts by weight of at least one of the low unsaturated rubber group and the high unsaturated rubber group. It is preferable to use a rubber composition containing 70 to 40 parts of at least one rubber.

[Function] The rubber composition constituting the outer layer contains a low unsaturation rubber of 30 to 30%.
Since it contains 60 parts by weight, it has excellent ozone crack resistance. Since the rubber composition constituting the inner layer contains 10 to 30 parts by weight of low unsaturation rubber, the adhesion with the outer layer is not inferior, and if the low unsaturation rubber is added to 15 to 30 parts by weight, Ozone crack resistance is also improved. Furthermore, since the rubber composition constituting the inner layer contains 90 to 70 parts by weight of highly unsaturated rubber, there is no inferiority in adhesion to a carcass or the like made of the highly unsaturated rubber composition. That is,
The inner layer is composed of a rubber composition blended with a composition intermediate between that of the outer layer and the carcass, so it acts as a buffer layer to prevent drastic changes in composition, and co-vulcanization with both is sufficiently performed.
Excellent adhesion.

If more than 70 parts by weight of highly unsaturated rubber is blended into the rubber composition constituting the outer layer, ozone crack resistance will be significantly reduced. If the amount is less than 40 parts by weight, there will be a large difference in the vulcanization reaction rate from the rubber layer mainly composed of highly unsaturated rubber, resulting in a significant decrease in adhesion and, at the same time, a decrease in flex fatigue resistance.

In the rubber composition constituting the inner layer, if the amount of highly unsaturated rubber is less than 70 parts by weight, the adhesive strength with a rubber layer mainly composed of highly unsaturated rubber such as a carcass will be insufficient for the same reason as above.

In addition, examples of halogenated butyl rubber, which is a type of low unsaturation rubber, include brominated butyl rubber, chlorinated butyl rubber, etc. Among them, the use of brominated butyl rubber improves the adhesion with high unsaturation rubber. . At that time, if more than 60 parts by weight of brominated butyl rubber is blended into the rubber composition constituting the outer layer, a decrease in tensile strength, processability, and dimensional stability may occur. If the amount is less than 20 parts by weight, sufficient ozone resistance and bending fatigue resistance may not be obtained. Furthermore, if more than 30 parts by weight of EPDM is blended, the adhesion to the rubber layer mainly composed of highly unsaturated rubber may be reduced, and the bending fatigue resistance may also be greatly reduced. 1
If the amount is less than 0 parts by weight, ozone resistance may be poor.

Furthermore, if more than 30 parts by weight of brominated butyl rubber is blended into the rubber composition constituting the inner layer, the adhesion to the rubber layer mainly composed of highly unsaturated rubber may decrease. EPD
The content of M is preferably 20 parts by weight or less from the viewpoint of adhesion to the rubber layer mainly composed of highly unsaturated rubber and bending fatigue resistance.

[Example] In order to confirm the improvement in ozone crack resistance in a rubber composition in which a part of the highly unsaturated rubber was replaced with a low unsaturated rubber, and the adhesion between the rubber compositions, the results shown in Table 1 were used. Rubber compositions were obtained by mixing according to the proportions (parts by weight), and their ozone resistance and discoloration properties were tested and are shown in Table 1. Also, the second
The adhesion between rubber compositions was tested using the combinations shown in the table.
The results are shown in the table.

The method for determining various physical properties will be described below.

a. Ozone test (evaluation of ozone resistance and discoloration) temperature 4
The time until crack generation and the degree of discoloration after 24 hours were measured at 0° C. in air containing a low ozone concentration of 50 pphm. Regarding the evaluation of discoloration, those with a clear difference were evaluated as major discoloration, those with some change were evaluated as discolored, those in between were evaluated as discolored, and those with no change were evaluated as unchanged.

b. Adhesion test (rubber-rubber adhesion evaluation) A sample made by stacking rubber sheets lined with organic fibers and molding them so that the rubber-rubber peeling is possible was molded using a plunger type mold.
After vulcanizing at 60° C. for 20 minutes and cutting into 1 cm wide pieces, the rubber-to-rubber adhesive strength was measured.

(Leaving space below) Table 2 ST: As shown in Table 1, the rubber composition CDEF containing 30 parts by weight or more of low unsaturation rubber has a high unsaturation rubber content of 10 parts by weight.
Compared to Rubber Composition A with a conventional formulation of 0 parts by weight, it has excellent ozone resistance and little or no discoloration.

However, as shown in Table 2, the rubber composition CDEF has a low adhesion to the rubber composition A, and such a rubber composition CDEF can be used to form a sidewall to a carcass made of the rubber composition A. Even if they come into contact, there is a high probability of separation between the sidewall and carcass during use.

However, when low unsaturation rubber is appropriately placed in both rubber compositions to be bonded, for example, rubber compositions C and B, C
and C, C, DSB, and D, when adjusting by mixing low unsaturated rubber so that the difference in high unsaturated rubber contained in the two to be bonded is 35 parts by weight or less, Increases adhesive strength.

Therefore, for the outer layer constituting the outer surface of the sidewall, a rubber composition containing 30 parts by weight or more of low unsaturation rubber is used to improve ozone resistance.
It is preferable to select the rubber compositions constituting the outer layer and the inner layer so that the difference in the content of highly unsaturated rubber between the inner layer and the carcass is 35 parts by weight or less.

Next, based on the above study, examples of formulations (Table 3) and combinations (Table 4) of rubber compositions constituting the outer layer and inner layer of the sidewall are shown.

All amounts are in parts by weight.

The method of determining various physical properties in each table is the same as that described above, but in the evaluation of rubber-to-rubber adhesion,
Evaluate the state of the peeling interface between the rubbers, and check for interfacial peeling!
, those that were cut without peeling were designated as ST, and those that partially peeled off at the interface were designated as 1-3T.

The composition of the carcass rubber whose adhesion to the outer layer or inner layer was evaluated in Table 3 is as follows.

(Parts by weight) Natural rubber 85 Butadiene rubber 15 Zinc white 5 Stearic acid 1 Anti-aging agent*1
2 Tackifier 1 Carbon Black (FEF) 40 Naphthenic Oil 8 Accelerator MSA” 1 Sulfur
2 *1: Same as anti-aging agent in Table 3 *2: N-oxydiethylene-2-benzothiazolesulfenamide (blank below) Table 4 Combination examples Next, using the drawings, the pneumatic tire of the present invention An example of this will be described.

(1) is a carcass with a radial structure. A sidewall (2) is disposed in close contact with the side surface of this carcass (1). The main part (5) of the sidewall (2) is
The thickness is uniform except for the embossed letters and symbols. In addition, this sidewall (2) has an inner layer (3) and an outer layer (4).
) is formed into a two-layer structure. Side wall (2)
The upper end (6) is disposed on the side surface of the tread rubber (8), extends and terminates while gradually decreasing in thickness. The lower end (7) of the sidewall has a structure in which the thickness gradually decreases and ends, and a rim strip (9) continues to this lower end (7). The inner layer of each of the main part (5), upper end part (6) and lower end part (7) contains 1 layer of low unsaturation rubber.
The rubber composition is comprised of 0 to 30 parts by weight and 90 to 70 parts by weight of highly unsaturated rubber. The outer layer of each of the main part (5), upper end part (6) and lower end part (7) contains 30 to 60 parts by weight of low unsaturated rubber and 70 parts by weight of high unsaturated rubber.
~40 parts by weight of a rubber composition.

As mentioned above, the inner layer (3) of the sidewall consists of a tread rubber (8) made of a highly unsaturated rubber composition, a carcass (
1) or the rim strip (9), the amount of low unsaturation rubber must be 30 parts by weight or less.

The tread rubber (8) is made of a highly unsaturated rubber composition as in the past, but it is reinforced with hard carbon black, which has a high reinforcing property, and has poor adhesion, so it is used as an inner layer rubber with less discoloration. It is preferable that the tread side rubber (10) made of a homogeneous rubber composition is placed on the side surface of the tread rubber (8) by coextrusion molding to improve adhesion to the sidewall.

In order to investigate the effect of the pneumatic tire of this example, the outer layer (4) of the sidewall (2) was composed of the rubber composition of Example 2 in Table 3, and the inner layer (3) was composed of the rubber composition of Example 5. Manufactured passenger car tires made of these materials. In addition, a conventional control tire was manufactured in which the sidewall was made of a single layer of the rubber composition of Comparative Example 1 in Table 3.

These tires were exposed to sunlight for one month under a south-facing eaves where rainwater would not come in contact with them, and discoloration of the sidewalls was examined. In the tire of this example, no bloom, discoloration, or cracking was observed. On the other hand, no cracks were observed on the side surface of the control tire, but blooming occurred and the color changed to reddish brown, significantly impairing the appearance. Using these tires exposed to sunlight, a drum test was conducted according to the durability performance test conditions described in JISD4230, and both the example tire and the control tire passed the test.

[Effects of the Invention] As described above, the pneumatic tire of the present invention improves the deterioration in aesthetic appearance due to discoloration of the side portions of the tire while maintaining tire durability and ozone resistance.

Furthermore, the present invention provides a pneumatic tire that uses a low unsaturation rubber and has a sidewall that is made of a diene rubber composition and has excellent adhesion to a carcass or the like.

[Brief explanation of the drawing]

The figure is an explanatory diagram of a meridian half cross section of a tire showing one embodiment of the present invention. Explanation of symbols (1)...Carcass, (2)...Side wall,
(3)...Inner layer, (4)...Outer layer, (5)...Main part, (6)...Upper end, (7)...Lower end, (8
)...Tread rubber, (9)...No change in the cleaning content of the rim strip drawing) Procedural amendment (method) August 5, 1988 1, Indication of case Patent application No. 128984 of 1988 2. Name of the invention ・ Pneumatic tire 3. Relationship with the case of the person making the amendment Patent applicant No. 17-18 Edobori 1-chome, Nishi-ku, Osaka (314) Toyo Rubber Industries Co., Ltd. Representative Hideo Matsushita 4, Agent 541 8th floor 6, Harada Building, 2-9 Kawaramachi, Higashi-ku, Osaka
, Correction target drawing

Claims (1)

[Claims] 1. A sidewall (2) that covers and protects the side surface of the carcass (1) has an inner layer (3) adjacent to the carcass (1);
In a pneumatic tire having a two-layer structure with an outer layer (4) disposed on the outside, the inner layer (3) contains at least one kind of low unsaturation rubber group consisting of halogenated butyl rubber and ethylene propylene diene rubber. ~30 parts by weight, and 90 to 70 parts by weight of at least one of the highly unsaturated rubber group consisting of natural rubber, isoprene rubber, butadiene rubber, and styrene-butadiene rubber, and the outer layer (4) is a rubber composition comprising 30 to 60 parts by weight of at least one member of the low unsaturation rubber group and 70 to 40 parts by weight of at least one member of the high unsaturation rubber group. A pneumatic tire characterized by: 2. The inner layer (3) contains 10 to 30 parts by weight of brominated butyl rubber, 0 to 20 parts by weight of ethylene propylene diene rubber, and 90 parts by weight of at least one of the highly unsaturated rubber group.
The outer layer (4) contains 20 to 60 parts by weight of brominated butyl rubber, 10 to 30 parts by weight of ethylene propylene diene rubber, and the highly unsaturated rubber. 70-40 at least one species of the group
2. The pneumatic tire according to claim 1, wherein the pneumatic tire is comprised of a rubber composition containing parts by weight. 3. The sidewall (2) that covers and protects the side surface of the carcass (1) with a radial structure has a two-layer structure consisting of an inner layer (3) adjacent to the carcass (1) and an outer layer (4) disposed outside of the inner layer (3). The upper end (6) of the sidewall is disposed on the side of the tread rubber (8) and extends while gradually decreasing in thickness until it ends, and the lower end (7) of the sidewall is disposed on the side of the tread rubber (8). The lower end (7) of this sidewall is followed by a rim strip (9) which gradually decreases in thickness, terminating at the lower end (7) of the sidewall (2) and at the upper end (6) of the main part (5).
The inner layer of each of the lower end portions (7) is made of a rubber containing 10 to 30 parts by weight of at least one of the low unsaturation rubber group and 90 to 70 parts by weight of at least one of the high unsaturation rubber group. The outer layer of each of the upper end (6), main part (5) and lower end (7) of the sidewall (2) contains at least one member of the low unsaturation rubber group in an amount of 30 to 60%. 3. The pneumatic tire according to claim 1, wherein the pneumatic tire is comprised of a rubber composition containing 70 to 40 parts by weight of at least one member of the group of highly unsaturated rubbers.