KR20030090961A - Tire captread rubber composition - Google Patents

Abstract

PURPOSE: A rubber composition for a tire cap tread is provided, to improve the abrasion resistance by employing the carbon black having specific characteristics and to allow the balance between the abrasion resistance and the resistance against exothermic property to be obtained by controlling the content and ratio of a curing agent. CONSTITUTION: The rubber composition comprises 100 parts by weight of a diene-based natural rubber; 45-55 parts by weight of carbon black having pH of 6-10, an iodine adsorption value of 120-125 mg/g, a nitrogen adsorption specific surface area of 130-140 m2/g, a dibutyl phthalate absorption of 120-130 ml/100 g, a coloring degree of 130-140 %, a weight average diameter (Dw) of 80-90 nm by centrifugal sedimentation, and ΔD50 of 50-60 nm; 2.0-3.0 parts by weight of a vulcanizing accelerator and sulfur in the ratio of 0.5-0.8 : 1 by weight; a curing activator; and an antiaging agent. Preferably the vulcanizing accelerator is N-cyclohexyl benzothiazole-2-sulfenamide or N-t-butylbenzothiazole sulfenamide.

Description

Tire captread rubber composition

The present invention relates to a rubber composition for a tire cap tread, and more particularly, to a rubber composition for a tire cap tread, which has a balance of wear resistance and heat resistance and can have a long life without an accident during use of a tire.

For large radial pneumatic tires used in trucks and buses, in order to prevent the explosion and separation of tires caused by heat generation of the tread during long-distance high-speed driving, it is necessary to increase the service life of the rubber composition itself. Wear resistance is important to balance at a high level.

As a method for improving the abrasion resistance of the tread rubber, it is common to use a carbon black as a reinforcing agent having a large specific surface area or a large structure in consideration of the difference in the structural characteristics of the carbon aggregates. An attempt was made to enhance the interaction between the polymers. In addition, methods for increasing the blending amount of carbon black have been taken to improve rubber reinforcement.

However, in general, when carbon black having a large specific surface area is used, reinforcement with rubber can be increased to achieve abrasion resistance, but it is generally known that the larger the specific surface area, the lower the heat generation resistance. Separation accidents can occur and cause significant performance problems during use of the product.

In addition, the method of increasing the blending amount of carbon black is inevitably reduced in heat resistance, and the unvulcanized viscosity due to the increase in the carbon black and polymer bonding phase also increases, and thus the workability is accompanied by a decrease in processability.

On the other hand, in general, as a method of lowering the heat generation of the rubber, a method of reducing the specific surface area of the carbon black used as a filler is widely used, but in this case, since the carbon black having a small specific surface area is used, the wear resistance of the composition is lowered, so that the entire tire It has resulted in reduced lifespan.

Therefore, in the present invention, while searching for a method for maintaining a balance between wear resistance and heat generation resistance, by using an appropriate amount of carbon black having a specific particle characteristics to improve the wear resistance, thereby compensating the heat resistance lowered by the vulcanizing agent content and As a result of adjusting the ratio, it has been found that the present invention can provide a rubber composition that has a balance of wear resistance and heat resistance and can have a long service life without an accident during tire use. That is, it is generally known that the heat resistance is improved as the crosslinking density is increased by adjusting the vulcanizing agent content. Therefore, the total content of sulfur and vulcanization accelerator is increased and the weight ratio of sulfur and vulcanization accelerator is appropriately selected to compensate for the heat resistance. The present invention was completed.

Accordingly, it is an object of the present invention to provide a rubber composition for a tire cap tread that has a balance of wear resistance and heat resistance and can have a long life without an accident during use of a tire.

The rubber composition for a tire cap tread of the present invention for achieving the above object comprises a diene-based natural rubber, carbon black, a vulcanization accelerator and sulfur, a vulcanization activator and an antioxidant, wherein the carbon black has a pH of 6 to 10 Iodine adsorption 120-125mg / g, nitrogen adsorption specific surface area 130-140m2 / g, dibutylphthalate absorption 120-130ml / 100g, coloring degree 130-140%, weight by centrifugal sedimentation The average diameter (Dw) is 80 to 90 nm and the half width of the maximum frequency (ΔD50) is 50 to 60 nm, it is included in 45 to 55 parts by weight based on 100 parts by weight of the diene-based natural rubber, the sulfur and vulcanization accelerator is sulfur It is characterized in that it comprises a total content of 2.0 to 3.0 parts by weight so that the weight ratio of the vulcanization accelerator to 0.5 to 0.8.

The present invention will be described in more detail as follows.

The rubber composition for the cap tread according to the present invention comprises 45 to 55 parts by weight of carbon black based on 100 parts by weight of the diene-based natural rubber, the carbon black used in the present invention has a pH of 6 to 10, iodine adsorption of 120 to 125 mg / g, the nitrogen adsorption specific surface area of 130 to 140 m 2 / g, the dibutyl phthalate absorption of 120 to 130 ml / 100 g, and the coloring degree of 130 to 140%. In addition, as agglomerate characteristics, the weight average diameter value (Dw) is 80-90 nm and the half value width ((DELTA) D50) of the maximum frequency diameter is 50-60 nm by the centrifugal sedimentation method.

When carbon black having such characteristics is blended in less than 45 parts by weight with respect to 100 parts by weight of diene-based natural rubber, satisfactory wear resistance is not obtained. In addition, when blended in excess of 55 parts by weight, the viscosity becomes high and workability is increased. It is difficult to expect the effect of complementing the heat generation resistance by adjusting the vulcanizing agent due to deterioration and excessive heat generation.

In addition, wear resistance is inferior when ordinary carbon black having no properties as described above, for example, having a specific absorption ratio surface area of 120 to 130 m 2 / g and a colorability of 120 to 130%.

On the other hand, in the present invention to adjust the vulcanizing agent content and ratio to compensate for the heat resistance to achieve a balance of wear resistance and heat resistance, specific weight ratio of the vulcanization accelerator and sulfur is 0.5 to 0.8, and the total vulcanization accelerator and sulfur The content is mixed so as to be 2.0 to 3.0 parts by weight based on 100 parts by weight of the diene natural rubber.

If the total content of sulfur and vulcanization accelerator used as a vulcanizing agent is less than the above-mentioned content, it is difficult to expect the effect of improving heat resistance due to the increase in the crosslinking density. .

In addition, when the weight ratio of the vulcanization accelerator and the sulfur exceeds the upper limit of the numerical range, the effect of complementing the heat resistance by adjusting the vulcanizing agent is decreased, and when the vulcanization agent is lower than the lower limit, the vulcanization efficiency is lowered and the vulcanization density decreases, which is not preferable. .

In the present invention, N-cyclohexylbenzothiazole-2-sulfenamide or N-t-butyl benzothiazolesulfenamide may be used as a vulcanization accelerator.

In addition, of course, the rubber composition for cap tread of the present invention can be appropriately blended with a vulcanization activator and an anti-aging agent used as a general rubber compounding agent.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Example 1

Next, a test piece of a rubber composition was prepared by a conventional method using a Banbary mixer and an open mill with the additives shown in Table 1 in the following composition ratios.

Comparative Examples 1 and 2

Next, the rubber composition was prepared in the same manner as in Example 1 using the compounding agent and the composition ratio of Table 1, and physical properties thereof were measured.

In Comparative Example 2, compared to Comparative Example 1, carbon black A was replaced with carbon black B having a relatively small particle size and a narrow aggregate size distrubution and high reinforcement.

The test pieces prepared according to Example 1 and Comparative Examples 1 to 2 were subjected to abrasion resistance test and heat generation test and the results are shown in Table 1 below.

Specific test methods are as follows.

Abrasion resistance test: A disk-shaped abrasive stone and the disk-shaped rubber composition test pieces of Examples 1 and 2 were rotated independently, respectively, and silicon carbide was dropped between the pressed abrasive stone and the rubber test piece to wear out of the rubber test piece. Table 1 shows the results of measuring the loss of abrasion of the rubber test piece, which prevents the surface from sticking to the abrasive stone and is caused by the difference in surface speed between the abrasive stone and the rubber test piece. The values shown in Table 1 below are the values shown using the value of Comparative Example 1 as a reference 100, and the higher the number, the better the wear resistance.

Heat resistance test: The rubber test pieces of Example 1 and Comparative Examples 1 and 2 were subjected to a strain of 10 Hz and 1% at 60 ° C. to measure the viscous modulus and elastic modulus at this time, and thus the ratio of these two values, namely, viscous modulus / elastic modulus The value of ie tan δ was calculated. The results measured by the rheometrics tester are shown in Table 1 below.

The value shown in the following Table 1 is a value shown by using the value of Comparative Example 1 as a reference 100, the smaller the number indicates that the heat resistance is disadvantageous.

Comparative Example Example One 2 One Natural rubber 100 100 100 Carbon Black A ⁽¹⁾ 50 - - Carbon Black B ⁽²⁾ - 50 50 Zinc oxide 3.5 3.5 3.5 Stearic acid 2.5 2.5 2.5 Antioxidant ⁽³⁾ 1.5 1.5 1.5 Antioxidant ⁽⁴⁾ One One One brimstone 1.2 1.2 1.5 NS ⁽⁵⁾ 1.1 1.1 0.9 NS / sulfur weight ratio 0.92 0.92 0.6 NS + Sulfur Total Content 2.3 2.3 2.4 Scorch time (minutes) 32 37 31 Abrasion Resistance Index 100 114 109 Fever Resistance Index 100 94 101 (1) Carbon Black A; (2) Carbon black B: pH 6-10, iodine adsorption 120-125 mg / g, nitrogen adsorption ratio surface area 130-140 m2. / g, dibutyl phthalate absorption 120-130ml / 100g, coloring degree 130-140%, weight average diameter (Dw) 80-90nm, (DELTA) D50 50-60nm. (3) N-phenyl-N ' -(1,3-dimethylbutyl) -p-phenylenediamine (4) poly- (2,2,4-trimethyl-1,2-dihydroquinoline) (5) Nt-butylbenzothiazole-2- Sulfenamide

From the results of Table 1, using only carbon black, such as carbon black used in the present invention, the content and compounding ratio of the vulcanizing agent compared to the conventional Comparative Example 2 has improved wear resistance compared to Comparative Example 1, but the heat resistance is lowered preferred The result is not.

Example 1 replaced carbon black A with carbon black B in Comparative Example 1, and adjusted the total content and weight ratio of sulfur and vulcanization accelerator in Comparative Examples 1 and 2, and Example 1 was Comparative Example 2. It can be seen that the wear resistance is slightly reduced compared to the fever resistance degradation. That is, Example 1 shows that wear resistance is improved and heat resistance is equivalent to that of Comparative Example 1, thereby achieving a balance between wear resistance and heat generation resistance, thereby improving overall tire life without accidents in use.

As described in detail above, in the case of replacing tire with carbon black having specific particle characteristics in the rubber composition for tire cap tread according to the present invention and adjusting the content and proportion of the vulcanizing agent, the tire is in use while balancing the wear resistance and the heat resistance. It is possible to provide a rubber composition which can have a long life without accident.

Claims (2)

In a tire cap tread rubber composition comprising a diene-based natural rubber, carbon black, a vulcanization accelerator and sulfur, a vulcanizing active agent and an anti-aging agent, The carbon black has a pH of 6 to 10, iodine adsorption of 120 to 125 mg / g, nitrogen adsorption specific surface area of 130 to 140 m 2 / g, dibutyl phthalate absorption of 120 to 130 ml / 100 g, and a coloring degree of 130 to 140%. In terms of characteristics, the weight average diameter (Dw) by centrifugal sedimentation method is 80 to 90 nm, and the half-width value (ΔD50) of the maximum frequency diameter is 50 to 60 nm, which is 45 to 55 parts by weight based on 100 parts by weight of the diene-based natural rubber. Wherein the sulfur and the vulcanization accelerator are contained in a total content of 2.0 to 3.0 parts by weight so that the weight ratio of the vulcanization accelerator to sulfur is 0.5 to 0.8. The rubber composition for tire cap tread according to claim 1, wherein the vulcanization accelerator is selected from the group consisting of N-cyclohexylbenzothiazole-2-sulfenamide and N-t-butyl benzothiazolesulfenamide.