JP3444814B2 - Rubber composition for tire tread - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition for a fuel-efficient tire tread that maintains grip performance.

[0002]

2. Description of the Related Art In addition to low fuel consumption, performance required for automobile tires is wide-ranging such as steering stability, wear resistance and riding comfort, and various measures have been taken. Among these performances, rolling resistance and grip performance are characteristics relating to hysteresis loss of rubber.

Generally, in order to increase the hysteresis loss, the glass transition temperature of rubber is raised, and the particle size of carbon black to be blended is made finer. As a result, the grip force is increased and the braking performance is improved. On the other hand, at the same time, rolling resistance also increases, which leads to an increase in fuel consumption. Further, a method of blending silica at a high filling rate has been proposed, but in this case, there is a problem that the workability of rubber is lowered.

Since the grip performance and the rolling resistance are in a contradictory relationship as described above, various rubber compositions for tire treads have been proposed in order to satisfy both properties at the same time.

As a technique for improving these problems,
For example, in EP 501227, a rubber composition for a tire tread having improved wet skid performance by a special silica and a device of kneading, and a method for producing the same,
Aluminum, which is disclosed in Japanese Patent Laid-Open No. 7-149950,
There is a rubber composition for a tire tread including 5 to 30 parts by weight of an inorganic compound powder having a particle diameter of 10 μm or less containing a metal oxide selected from magnesium, titanium and calcium, or a metal hydroxide. However, in the former case, there is a problem in the workability of the rubber, and the electric resistance is increased to generate static electricity. On the other hand, with regard to the latter, there is a problem that the obtained rubber composition for tire tread has insufficient abrasion resistance and fracture characteristics.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition for a tire tread, which maintains rolling resistance without lowering workability and wear resistance and improves wet skid performance. To do.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned conventional problems, the inventor of the present invention maintained the rolling resistance by adding a specific inorganic compound having a high specific gravity to a rubber component. The inventors have found that it is possible to obtain a rubber composition for a tire tread that improves wet skid performance, and have completed the present invention.

Namely, the invention of claim 1, with respect to natural rubber and / or diene rubber 100 parts by weight of tungsten powder, zinc powder, zirconium powder, zirconium silicate, from zirconium and barium sulfate Powder or Ranaru group A rubber composition for a tire tread, which comprises 5 to 35 parts by weight of an inorganic compound powder having a specific gravity of 3.5 or more and an average particle diameter of 20 μm or less, and 30 to 110 parts by weight of carbon black, which is composed of at least one selected from Is.

According to a second aspect of the present invention, the carbon black has a nitrogen adsorption specific surface area of 70 m ² / g or more, and DB
The rubber composition for a tire tread according to claim 1, which is carbon black having a P oil absorption of 90 ml / 100 g or more.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component of the present invention is a natural rubber and / or a diene rubber. Examples of the diene rubber include styrene butadiene rubber, polybutadiene rubber, polyisoprene rubber and the like, and a mixture of these can also be used. The average particle diameter of the inorganic compound powder of the present invention is 20 μm or less, preferably 0.05 to 10 μm, and more preferably 0.1 to 4 μm.
μm is desirable. If the average particle size of the inorganic compound powder exceeds 20 μm, the wear performance and the cut chipping performance deteriorate, which is not preferable. The specific gravity of the inorganic compound powder is 3.5 or more, preferably 4 to 2
It is 0, more preferably 7 to 20. If the specific gravity is less than 3.5, the volume of the inorganic compound powder in the rubber will be large and the abrasion resistance will be poor.

Preferred as the inorganic compound powder are tungsten powder, zinc powder, zirconium powder, zirconium silicate, zircon, barium sulfate powder, zinc white, zinc oxide powder, titanium oxide powder and the like. These can be used alone or as a mixture of two or more.

The compounding amount of the inorganic compound powder is natural rubber and / or diene rubber (hereinafter referred to as "rubber component").
The amount is 5 to 35 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight. The compounding amount of the inorganic compound powder is 5
Wet skid performance is insufficient if less than 35 parts by weight,
If it exceeds the parts by weight, the wear resistance is reduced.

The carbon black of the present invention has a nitrogen adsorption specific surface area of 70 m ² / g or more, preferably 100 to 2
00m ² / g and DBP oil absorption 90ml / 10
It is 0 g or more, preferably 100 to 169 ml / 100 g. The DBP oil absorption is measured according to JIS K622.
1 Oil absorption A method.

When the nitrogen adsorption specific surface area is less than 70 m ² / g, sufficient abrasion resistance cannot be obtained when the inorganic compound powder is blended, and when the DBP oil absorption is less than 90 ml / 100 g,
Similarly, sufficient abrasion resistance cannot be obtained when an inorganic compound powder is blended.

The compounding amount of carbon black is the rubber component 1
30 to 110 parts by weight, preferably 3 to 100 parts by weight
It is 5 to 95 parts by weight, more preferably 40 to 90 parts by weight. If the amount of carbon black is less than 30 parts by weight, the abrasion resistance will decrease, and if it exceeds 110 parts by weight, the workability will decrease.

The rubber composition for tire tread of the present invention is
It can be obtained by kneading the rubber component, the inorganic compound powder, and the carbon black with an ordinary processing device such as a roll, a Banbury mixer, or a kneader.
Further, in the rubber composition for a tire tread of the present invention, in addition to the above components, a compounding agent usually used as a rubber compounding agent, for example, a process oil, a vulcanizing agent, an antiaging agent or the like can be appropriately compounded. .

[0017]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The following raw materials were used in Examples and Comparative Examples.

Tungsten powder: Tokyo Tungsten Co., Ltd. C50H average particle size 3 μm specific gravity 19.3 Zinc powder A: Toho Zinc Co., Ltd. AN-325 average particle size 18 μm specific gravity 7.1 Zinc powder B: Toho Zinc Co., Ltd. ) Manufactured by AN-80 average particle size 80 μm specific gravity 7.1 Silica: manufactured by Degussa Ultrasil VN3 aluminum hydroxide: manufactured by Sumitomo Chemical Co., Ltd. CL301 average particle size 1.4 μm specific gravity 2.4 N351: carbon black Mitsubishi Chemical (stock) ) DBP oil absorption amount 126 ml / 100 g Nitrogen adsorption specific surface area 84 m ² / g N326: carbon black Mitsubishi Chemical Corporation DBP oil absorption amount 74 ml / 100 g Nitrogen adsorption specific surface area 84 m ² / g

The evaluation methods used in the examples and comparative examples will be summarized below.

(Wet skid performance) A braking distance from an initial speed of 64 km / h was obtained on a wet asphalt road surface. The tire size was 185 / 65R14, and the test vehicle was a domestic FF vehicle. The result is expressed by an index, and the larger the number, the better the wet skid performance. The index was calculated by the following formula. Wet skid performance = (braking distance of each example or comparative example) / (braking distance of comparative example 1) × 100

(Abrasion resistance) A tread was attached to a domestic FF vehicle and the tire tread was 1 m after running 15,000 km on the pavement.
The traveling distances at the time of wear were compared, and Comparative Example 1 was set as 100 and indicated as an index. The larger the index, the better the wear resistance and workability.

(Rolling resistance) The rolling resistance was measured by a conventional method under the conditions of a load of 4.66 kilonewtons, an internal pressure of 200 kilopascals, and a speed of 80 km / h.
It was displayed as an index when it was set to. The higher the number, the lower the rolling resistance.

(Workability) The workability was evaluated by the Mooney viscosity. The Mooney viscosity was measured at 130 ° C. using a Mooney viscometer (manufactured by Shimadzu Corporation). The test method is J
According to IS K6300, ML _{1 + 4} (after 1 minute preheating, 4
The Mooney viscosity value after the minute operation was calculated and compared.

Examples 1 and 2 and Comparative Examples 1 to 7 According to the compounding formulation (compounding unit: parts by weight) of Table 1, compounding agents other than sulfur and a vulcanization accelerator and raw rubber are mixed with a Banbury type internal mixer. Then, sulfur and a vulcanization accelerator were added to the obtained masterbatch on an open roll to prepare a rubber composition for a tire tread. An evaluation test of workability was performed on each rubber composition for tire tread.
Next, Examples 1 to 1 are applied to the tire tread of a pneumatic tire.
Using the rubber compositions of No. 2 and Comparative Examples 1 to 7, evaluation tests were conducted for wet skid performance, abrasion resistance, and rolling resistance. The results of these evaluation tests are shown in Table 1.

[0025]

[Table 1]

Examples 1 and 2 are rubber compositions for tire treads in which 100 parts by weight of the rubber component is mixed with the inorganic compound powder and carbon black within the scope of the present invention. It can be seen that these have improved wet skid performance while maintaining rolling resistance, workability, and wear resistance. The control was Comparative Example 1.

Comparative Example 2 is an example in which an inorganic compound powder having a specific gravity outside the range of the present invention was blended. The wet skid performance was improved but the wear resistance was poor.

Comparative Examples 3 and 4 are examples in which silica, which is an inorganic compound powder outside the scope of the present invention, is blended, and Comparative Example 4 in which a large amount of silica is blended has poor processability, and a comparative example in which a small amount of silica is blended. In Example 3, the rolling resistance was low and the workability was poor.

Comparative Example 5 is an example in which the glass transition temperature of rubber is increased by using SBR having a large amount of styrene. In this case, wear resistance and rolling resistance were lowered.

Comparative Example 6 is an example in which the particle size of the inorganic compound powder falls outside the range of the present invention, but the wear resistance was poor.

[0031] Comparative Example 7, carbon black specified value (nitrogen adsorption specific surface area and D BP oil absorption) is a and the wear resistance is lowered example using what is outside the scope of the present invention.

[0032]

EFFECTS OF THE INVENTION According to the present invention, a rubber composition for a tire tread is obtained which maintains rolling resistance without lowering workability and wear resistance and improves wet skid performance.

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Claims (2)

(57) [Claims] 1. Natural rubber and / or diene rubber 1
Against 00 parts by weight, tungsten powder, zinc powder, zirconium powder, zirconium silicate, zircon Contact
At least one consisting of or more, a specific gravity of an average particle size of less inorganic compound 20μm powder 5-35 parts by weight 3.5 or more and carbon black from 30 to 110 parts by weight selected from the group Ranaru or powder barium sulfate powder and A rubber composition for a tire tread, which comprises: 2. The carbon black has a nitrogen adsorption specific surface area of 70 m ² / g or more and a DBP oil absorption of 90 m.
The rubber composition for a tire tread according to claim 1, which is carbon black of 1/100 g or more.