JP2662281B2 - Rubber composition for large tire tread - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a rubber composition for a large tire tread, and more particularly, to an improvement in wear resistance of a large tire for trucks and buses, which can greatly improve the tire life. The present invention relates to a rubber composition for a tread.

(Prior art) Conventionally, techniques for improving the wear resistance of large tires include increasing the amount of carbon black, increasing the amount of butadiene rubber (BR) added, and reducing the amount of softener such as process oil. Has been adopted.

(Means for Solving the Problems) However, techniques for improving wear resistance which have been conventionally adopted have not always been satisfactory.

That is, as the amount of carbon black in the rubber is increased, the wear resistance can be improved within a certain compounding range as conventionally understood. As a result, the improvement effect is reduced. Further, when the blending amount of carbon black is increased, heat generation is reduced and workability is lowered due to increase in plasticity.

Also, an increase in the amount of butadiene rubber can improve abrasion resistance, especially high input abrasion resistance, but this technique alone cannot be said to be sufficient when the life of a large tire is to be improved.

Furthermore, although the reduction in the amount of the softening agent such as process oil can improve the abrasion resistance, it deteriorates the consistency of the kneaded rubber and lowers the workability due to an increase in plasticity.

On the other hand, carbon blacks having a smaller particle size and a higher proportion of aggregates (structures) having a chain structure are known. For example, Japanese Patent Application Laid-Open No. 62-277446 discloses a nitrogen black specific surface area (N ₂ SA). ) technology that a DBP oil absorption 130m ² / g~160m ² / g to apply carbon black 110~150ml / 100g natural rubber alone rubber composition have been developed. However, the hysteresis loss is large in the natural rubber alone system, and in this system, the effect of improving the wear resistance of the carbon black cannot be obtained.

Therefore, an object of the present invention is to provide a rubber composition for a tread which can further improve the wear resistance of a large truck and bus tire as compared with the prior art and can greatly improve the tire life. .

(Means for Solving the Problems) The hysteresis loss can be reduced by lowering the loss coefficient tan δ value of rubber, and such a reduction in the hysteresis loss causes a reduction in the wear coefficient. In addition, the dynamic storage modulus E '
When the height is increased, invasion of foreign matter and the like from the road surface can be prevented, and the wear resistance can be improved. It is thought that carbon black having a high structure and a small particle diameter can balance these properties and improve wear resistance.However, as described above, the natural rubber alone has a high hysteresis loss, and the effect of improving the wear resistance is sufficiently improved. Therefore, the present inventors have conducted intensive studies to find a rubber system capable of reducing the tan δ value with such carbon black. as a result,
It has been found that when an optimum amount of a butadiene rubber and a natural rubber / isoprene rubber is used in a blend system, the abrasion resistance can be remarkably improved by the synergistic effect of the carbon black, and the present invention has been completed.

That is, the present invention relates to 15 to 70 parts by weight of butadiene rubber (BR) and natural rubber (NR) and / or isoprene rubber (I).
R) For 100 parts by weight of the rubber component consisting of 30 to 85 parts by weight,
Cecil bromide (CTAB) adsorption specific surface area 140~150m ² / g and dibutyl phthalate (DB
P) A rubber composition for a large tire tread, comprising 30 to 75 parts by weight of carbon black having an oil absorption of 130 to 150 ml / 100 g.

The rubber composition of the present invention has a dynamic storage modulus E ′ of 1.00.
× 10 ^{8 to} 1.35 × 10 ⁸ kg / cm ² and loss factor tanδ value is 0.23 to 0.2
Preferably it is 8.

The amount of butadiene rubber is preferably 35 to 70 parts by weight.

In the rubber composition of the present invention, compounding agents usually used in the rubber industry, for example, a softening agent, an antioxidant, a vulcanization accelerator, a vulcanization accelerator, a vulcanizing agent, a reinforcing filler and the like. Needless to say, it can be appropriately compounded within the usual range of the compounding amount as required.

(Operation) In the blend system of BR and NR / IR in the present invention, the carbon black according to the present invention increases the E ′ value by reducing the particle size and decreases the tan δ value due to the improvement in heat generation due to the high structure. It is thought to cause.
In other words, in the above-mentioned blended rubber system, the reduction of the particle size and the structure of the carbon black are caused by the increase in the E ′ value and the ta value.
It can be said that there is an effect of balancing the two points of the decrease of the nδ value. This effect is largely related to the factor of hysteresis loss (μ _H ) among the friction coefficients, which increases the E ′ value and increases tan.
Decreasing the value of δ causes a decrease in the coefficient of friction, which means that the amount of wear is reduced.

In the present invention, it is necessary to use a blend rubber system in which 15 to 70 parts by weight of butadiene rubber (BR) is blended. The reason for this is that if BR is less than 15 parts by weight per 100 parts by weight of the rubber component, a BR blending effect is exhibited. This is because the effect of improving the wear resistance is insufficient without using it, and when it exceeds 70 parts by weight, the appearance is poor and it cannot be used.

Incidentally, the BR polymerized using the Co catalyst is Li, compared to the BR polymerized using the Nb catalyst, the abrasion resistance improving effect when combined with the carbon black according to the present invention is larger,
preferable.

The carbon black used must have a CTAB adsorption specific surface area and a DBP oil absorption within a predetermined range for the following reason.

First, regarding the CTAB adsorption specific surface area, if this is less than 140 m ² / g, the particle size becomes too large and the wear resistance is insufficient,
On the other hand, if it exceeds 150 m ² / g, it becomes too hard to work.

Next, as for DBP oil absorption, if this value is less than 130 ml / 100 g, the proportion of the structure becomes too small and the wear resistance is insufficient, while if it exceeds 150 ml / 100 g, the fatigue resistance deteriorates and the appearance deteriorates and it can not be used Becomes

Although the compounding amount of such carbon black is required to be in the range of 30 to 75 parts by weight based on 100 parts by weight of the rubber component,
The reason for this is that if the amount is less than 30 parts by weight, the carbon black cannot be reinforced and the wear resistance is not good, whereas if it exceeds 75 parts by weight, the carbon black disperses poorly and processing during tire production becomes impossible. is there.

The rubber composition of the present invention has a loss factor tan δ value of 0.230 to 0.28.
In the 0 range, the dynamic storage modulus E ′ value is 1.00 × 10 ^{8 to} 1.35 × 10 ⁸ k
g / cm ² is preferred. This is because these values have an effect on hysteresis loss (μ _H ). By setting the content within such a predetermined range, the effect of improving the wear resistance is increased. Because.

(Examples) Next, the present invention will be specifically described with reference to examples.

The following physical properties were measured for each rubber composition having the mixing ratio (parts by weight based on 100 parts by weight of the rubber component) shown in Table 1 below.

CTAB adsorption specific surface area It carried out based on ASTM D-3765-85.

DBP oil absorption This was carried out in accordance with the JIS K6221-1982A method.

E 'and tan δ Using a viscoelastic spectrometer manufactured by Iwamoto Manufacturing Co., Ltd.
The measurement was performed at room temperature under the conditions of an initial strain of 5%, a dynamic strain of 2%, and a frequency of 50 Hz.

Next, using these rubber compositions for the tread, TBR1000R20
Test tires of 14 PR R210 Z were manufactured, and the wear resistance of these tires was evaluated. Evaluation method is about 100,000km
The running distance per 1 mm of wear is calculated from the average of the groove depth after running. In accordance with the above, Comparative Example 1 was set to 100 and indicated by an index. The higher the value, the better the result.

 The results obtained are shown in Table 1.

(Effects of the Invention) As can be seen from the measurement results in Table 1, in each of the rubber compositions satisfying the requirements of the present invention, the abrasion resistance was significantly improved without impairing workability and appearance. Therefore,
The rubber composition of the present invention can greatly improve the life of large tires.

Claims (3)

(57) [Claims] 1. A rubber component consisting of 15 to 70 parts by weight of butadiene rubber and 30 to 85 parts by weight of natural rubber and / or isoprene rubber, 100 parts by weight of cesyltrimethylammonium bromide (CTAB) adsorption specific surface area of 140 to 150 m ^A rubber composition for a large tire tread, comprising 30 to 75 parts by weight of carbon black having a ² / g and dibutyl phthalate (DBP) oil absorption of 130 to 150 ml / 100 g. 2. A dynamic storage modulus E 'value is 1.00 × 10 ⁸ ~1.35
The rubber composition according to claim 1, wherein the rubber composition has a loss coefficient tan δ value of 0.23 to 0.28 at × 10 ⁸ kg / cm ² . 3. The rubber composition according to claim 1, wherein 35 to 70 parts by weight of butadiene rubber is compounded.