JP2001261886A - Rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition having improved processability while maintaining low heat build-up, good fracture characteristics and low temperature properties at the natural rubber level, and a pneumatic tire to which the rubber composition is applied. SOLUTION: The rubber composition comprises a rubber component composed of (A) 10-30 pts.wt. styrene/butadiene copolymer rubber and (B) 90-70 pts.wt. natural rubber, and the styrene/butadiene copolymer rubber as component (A) being a copolymer rubber by solution polymerization which, at the same time, has an amount of bonded styrenes of 4-8 wt.% and a content of vinyl bonds in the remaining butadiene portions of 25-40%, and the pneumatic tire has a belt insulation rubber or the like to which this rubber composition is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition and a pneumatic tire, and more particularly, to a tire inside a tire such as a coating rubber for a carcass and a belt in a vehicle tire used at a high speed and a high load such as an aircraft or a linear motor car. The present invention relates to a rubber composition suitable for use as a constituent member and a pneumatic tire to which the rubber composition is applied.

[0002]

2. Description of the Related Art In general, high-speed and high-load tires are used under high internal pressure, high load and high-speed conditions, and therefore require higher durability than tires in other fields. In particular, when an aircraft tire lands, the load on the tire is large. Also, in the case of a linear motor car, the load on the tires is large even in the unlikely event that a vehicle levitating at high speed is forced to make an emergency landing due to an unexpected situation. As described above, when a high load is applied to the tire, the heat generated inside the tire is significantly increased. As a result, the tread rubber having a small heat transfer coefficient accumulates heat and becomes high temperature, and particularly, each internal component of the crown portion. In this case, there is a possibility that a rubber destruction failure due to re-vulcanization, which is referred to as a blow-out, may occur. For this reason, conventionally, natural rubber having low heat build-up and good breaking resistance has been used alone for rubber for internal components such as carcass and belts of aircraft tires and linear motor car tires. Also, as an aircraft, it is necessary to consider the temperature drop in the air during the flight, but natural rubber is also advantageous in that it has a low glass transition temperature. However, since natural rubber has a high viscosity, workability (fluidity) is inferior when organic rubber is coated with a rubber having a predetermined thickness. Therefore, further improvement in tire productivity is required. Improvement was desired.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has improved processability while maintaining low heat build-up, fracture resistance and low-temperature characteristics at the same level as natural rubber. An object of the present invention is to provide a rubber composition and a pneumatic tire to which the rubber composition is applied.

[0004]

Means for Solving the Problems As a result of diligent studies to achieve the above object, the present inventor has found that natural rubber and styrene-butadiene having specific properties are used as rubber components of a rubber composition used for a tire. It has been found that the above object can be achieved by using a blend of a polymer rubber. (1) That is, the feature of the present invention is that the rubber component is (A)
A rubber composition comprising 10 to 30 parts by weight of a styrene-butadiene copolymer rubber and 90 to 70 parts by weight of (B) a natural rubber, wherein the styrene-butadiene copolymer rubber as the component (A) is: A copolymer rubber obtained by solution polymerization, wherein the copolymer rubber has a bound styrene content of 4 to 8% by weight and a vinyl bond content in the remaining butadiene portion of 25 to 40%. The object of the present invention is to provide a rubber composition. (2) Further, the present invention is characterized in that a pair of beads, a carcass connected to the beads in a toroidal shape, a belt layer and a tread located outside a crown of the carcass, In the tire where the belt uppermost layer and the cut protector buried at a distance from the
Another object of the present invention is to provide a pneumatic tire characterized in that the rubber composition constituting the tire inner member comprises the rubber composition of the above (1). Here, the tire inner member includes:
It is preferably at least one of a carcass, a belt, a belt insulation rubber, and a cut protector.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the rubber composition of the present invention, a rubber component comprising 10 to 30 parts by weight of a styrene-butadiene copolymer rubber (SBR) and 90 to 70 parts by weight of a natural rubber is used. The reason for this is that if the SBR is less than 10 parts by weight, the effect of improving the processability, especially the fluidity, is too small, and if it exceeds 30 parts by weight, the fracture resistance of the rubber deteriorates. Further, other rubber components can be contained as long as the effects of the present invention are not impaired. In the rubber composition of the present invention, the reason why the SBR is a solution-polymerized copolymer rubber is that the low-temperature properties and processability of the rubber composition are superior to those obtained by emulsion polymerization. The reason why the amount of bound styrene of the copolymer rubber is set to 4 to 8% by weight is 4% by weight.
If it is less than 10%, the effect of improving workability is small, and if it exceeds 8% by weight, the glass transition point becomes high. The content of vinyl bonds in the butadiene portion of the copolymer rubber is 25.
The reason why it is set to 40% is that if it is less than 25%, the effect of improving heat resistance is small, and if it exceeds 40%, the glass transition point becomes too high.

[0006] The styrene-butadiene copolymer rubber is preferably one which is coupled with a tin-containing compound. This is because, when coupling is performed with a tin-containing compound, the processability of the rubber composition is significantly improved and low heat build-up is better than when other coupling agents are used. Here, a styrene-butadiene copolymer rubber coupled with a tin-containing compound is disclosed in JP-A-63-179.
It can be manufactured by a known method such as Japanese Patent No. 949. For example, it is produced by obtaining a copolymer of styrene and butadiene in a hydrocarbon solvent using an organic lithium catalyst, and then reacting the active terminal of the copolymer with a tin-containing compound. Examples of the tin-containing compound include tin halide compounds such as tin tetrachloride and tin tetrabromide; and organotin halide compounds such as diethyldichlorotin, dibutyldichlorotin, tributyltin chloride, diphenyldichlorotin, and triphenyltin chloride. Is mentioned. Further, in the rubber composition of the present invention, further, the average particle size is 25 to 30 nm, the specific surface area of cetyltrimethylammonium bromide (CTAB) is 60 to 80 m ² / g,
Dibutyl phthalate (DBP) carbon black having an absorption amount of 95 to 110 ml / 100 g was added to rubber component 1
It is preferable to add 30 to 50 parts by weight to 00 parts by weight. If the average particle size of the carbon black is less than 25 nm, low heat build-up and workability may not be sufficient,
If it exceeds nm, the fracture resistance may not be sufficient.
The CTAB specific surface area and the DBP absorption amount are A
This is a value obtained based on STM D3765 and D2414. The rubber composition of the present invention contains reinforcing or non-reinforcing fillers, softeners, anti-aging agents, vulcanizing agents, vulcanization accelerators, vulcanization accelerators, etc. An agent can be appropriately compounded.

FIG. 1 shows an aircraft radial tire according to an embodiment of the present invention. In this tire, a pressure vessel is formed by a carcass 6 that keeps the internal pressure of the air supplied inside. The carcass 6 has a horseshoe shape and industrial fibers (for example, nylon, polyester, aramid, etc.), and a plurality of steel wire cords arranged as desired.
The cord is covered with a rubber composition. The tire has a radial structure in which the axial direction of the cords of the carcass 6 is substantially along the width direction of the tire, and these cords are arranged in the tire circumferential direction. A belt layer 3 located outside the crown portion of the carcass 6, a tread portion outside the crown layer, and a cut protector layer 1 embedded in the tread portion at a distance from the uppermost layer of the belt are arranged. The carcass 6 forms a sidewall portion on the side surface portion of the tire. Both ends of the carcass 6 are wound and held around bead cores arranged around the tire rotation axis.

Further, a cut protector 1 as a reinforcing layer is embedded in the tread portion at a distance from the tread side of the uppermost layer of the belt layer. Cut protector 1
It is a knitted type of industrial fiber cord such as aramid cord, which is covered with a rubber composition and serves to protect the belt 3 from transmitting the progress of cutting from the surface of the tread damaged by ground contact with the ground. have. Further, a space rubber 5 is provided near the belt end, and a second stiffener 7 is provided between the carcass ply 6 and the rubber chafer 9 outside the first stiffener 8. In the present invention, the rubber composition is applied to any of a carcass coating rubber, a belt coating rubber, a coating rubber for a cut protector, and a belt insulation rubber 4 disposed between the belt 3 and the carcass ply 6. It is particularly preferable to apply to belt insulation rubber. In this way, a pneumatic tire having excellent durability can be efficiently manufactured with good workability.

[0009]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited by these examples. [Various Measurement Methods] The performance of various samples was evaluated according to the following methods.

(1) Low heat generation (resilience) British Standard 903: Part A
8: Calculated by the following equation from a rebound resilience test performed according to 1963. Low heat buildup index = {Rebound resilience of test specimen / Rebound resilience of test specimen of Comparative Example 1 (control) using only natural rubber}
× 100 The larger the low heat build-up index, the better the heat build-up, that is, the smaller the calorific value. (2) Fracture resistance load: 159 kg (350 LB), rotation speed: 200 rpm,
At room temperature, a dynamic shear test was performed to measure the time required for the specimen to undergo fatigue fracture, and this was used as an index of the fracture resistance. The evaluation is represented by an index with Comparative Example 1 (control) taken as 100, and the larger the index, the better the fracture resistance. (3) Workability Here, the workability refers to the workability when coating the organic fiber with the rubber composition having a predetermined thickness, and the evaluation is made based on the coating (at the time of insulation or calendar) speed. It is indicated by an index with Comparative Example 1 (control) taken as 100, and the larger the index, the better the workability.

Comparative Examples 1 to 5 and Examples 1 to 4 The mixing ratio of each component in the rubber compositions of Comparative Examples 1 to 5 and Examples 1 to 4, the amount of bound styrene in SBR and the vinyl bond in the butadiene portion Is shown in Table 1. The carbon black used in each of Comparative Examples and Examples had a particle size of 28 nm and a CTAB specific surface area of 70.
m ² / g, DBP absorption 100ml / 100g
Met. Rubber test pieces were prepared from the rubber compositions of Comparative Examples and Examples, and the physical properties (1) to (3) were evaluated.
Table 1 shows the results.

[0012]

[Table 1]

[0013]

[Table 2]

As shown in Table 1, Comparative Example 1 is a rubber composition comprising only natural rubber as a control. Comparative Examples 2 to 5 are examples in which the amount of bound styrene is outside the range of 4 to 8% by weight and no coupling agent is used, and Comparative Example 3 is an example in which the content of vinyl bonds in the butadiene portion is more than 40%. In any case, the workability is improved, but the low heat build-up and the fracture resistance are deteriorated. On the other hand, in Examples 1-4 satisfying all the constituent requirements of the present invention, workability is also improved while low heat build-up and fracture resistance are improved as compared with Comparative Example 1. In particular, in Examples 1 to 3 using tin tetrachloride as the coupling agent, the processability was significantly improved.

[0015]

As described in detail above, the rubber composition of the present invention has improved processability while maintaining low heat build-up, fracture resistance and low-temperature characteristics at or above those of natural rubber. The rubber composition is useful as a rubber composition for carcasses, belts, belt insulation rubbers, cut protectors, and the like of vehicle tires used at high speed and high load. It can be suitably applied to tires.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an example of a pneumatic tire of the present invention.

[Explanation of symbols]

 1: Cut protector 2: Cushion rubber 3: Belt 4: Belt insulation rubber 5: Space rubber 6: Carcass ply 7: Second stiffener 8: First stiffener 9: Rubber chafer

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Claims (7)

[Claims] 1. A rubber component comprising: (A) 10 to 30 parts by weight of a styrene-butadiene copolymer rubber; and (B) natural rubber 9
A rubber composition comprising 0 to 70 parts by weight, wherein (A)
The styrene-butadiene copolymer rubber as a component is a copolymer rubber obtained by solution polymerization, and the copolymer rubber has a bound styrene amount of 4 to 8% by weight, and has a vinyl bond in the remaining butadiene portion. Content is 25-4
A rubber composition characterized by being 0%. 2. The rubber composition according to claim 1, wherein the styrene-butadiene copolymer rubber is coupled with a tin-containing compound. 3. A cetyltrimethylammonium bromide having an average particle size of 25 to 30 nm and a specific surface area of 60 to 80 m ^2.
/ G, dibutyl phthalate absorption amount of 95 to 110 ml / 100 g of carbon black was added to rubber component 100
The rubber composition according to claim 1, wherein 30 to 50 parts by weight is blended with respect to part by weight. 4. A pair of bead portions, a carcass connected to the bead portions in a toroidal shape, a belt layer and a tread portion located outside a crown portion of the carcass, and a belt uppermost layer in the tread portion. In a tire provided with a cut protector buried at a distance, the rubber composition constituting the tire internal member comprises the rubber composition according to any one of claims 1 to 3. Pneumatic tires. 5. The tire according to claim 5, wherein the rubber inside member is a carcass,
The pneumatic tire according to claim 4, wherein the pneumatic tire is at least one of a belt, a belt insulation rubber, and a cut protector. 6. The pneumatic tire according to claim 4, wherein the pneumatic tire is a vehicle tire used under high speed and high load. 7. The pneumatic tire according to claim 4, which is a tire for an aircraft or a linear motor car.