JPH0625473A - Rubber composition - Google Patents

Abstract

PURPOSE:To provide a rubber compsn. having an enhanced stiffness without detriment to the characteristics such as a low heat build-up, a high tear resistance, and a good adhesion to a steel cord. CONSTITUTION:A rubber compsn. is prepd. by compounding 100 pts.wt. rubber component with 50-70 pts.wt. carbon black which comprises a carbon black satisfying the relations :80<=CATB<=110, 65<=24M4DBP<=75, and N2SA/IA>=1.1 and a carbon black satisfying the relation :100<=CATB<=140 in a wt. ratio of (100:10) to (100:100).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber composition.

[0002]

2. Description of the Related Art Generally, in order to improve the durability performance of a product that receives a dynamic strain or a static strain such as an automobile tire,
It is necessary to reduce the strain on the tire. For radial tires, the belt layer rubber compound covering the steel cord and the carcass ply rubber compound cause shear strain between the steel cord and those rubbers during tire running, and the strain causes rubber fracture and adhesive fracture. This eventually causes tire separation. Considering the relative rigidity difference between the rubber compound that covers high rigidity such as this steel cord and the cord, the higher the rigidity, the smaller the shear strain of the rubber compound itself, which is advantageous in terms of separation resistance. It is believed that there is.

In recent years, with the improvement of highways and the higher performance of vehicles (higher speed, higher horsepower, etc.), the chances of traveling at high speed for a long time have increased, and the strain on tires has increased.
Development of a rubber composition having higher rigidity than ever before is desired.

In order to increase the rigidity, it has been studied to increase the amount of carbon black blended in the rubber composition, blend carbon black having a small particle size, blend a large amount of sulfur, and the like. However, when the amount of carbon black is increased, the heat generation property is deteriorated, the durability of the tire is deteriorated, the tear fracture property is deteriorated, and the workability is also deteriorated. When carbon black having a small particle size is blended, there arises a drawback that heat generation and workability are deteriorated. Further, when a large amount of sulfur is blended, there is a drawback that heat deterioration is likely to occur due to heat generated during running and the life of the tire is shortened.

The rubber composition covering the steel cord and the rubber composition used in the periphery thereof have not only high rigidity but also low exothermic property, high tear fracture property, and steel. It is required to have characteristics such as good adhesion to the cord. However, under the present circumstances, it is unavoidable that other properties such as heat generation property and tear fracture property are deteriorated when the rigidity is increased as described above.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition capable of enhancing only rigidity without deteriorating properties such as low heat buildup, high tear fracture properties, and adhesion with steel cord. Especially.

The present inventors have conducted extensive research to develop a rubber composition that meets the above-mentioned needs. As a result, they have found that the desired object of the present invention can be achieved when the following two types of carbon black are compounded in a rubber component in a specific ratio in a specific amount. The present invention has been completed based on such knowledge.

That is, according to the present invention, (A) 80≤CATB≤
110, 65 ≦ 24 M4DBP ≦ 75 and N ₂ SA / I
Carbon black satisfying A ≧ 1.1 and (B) 100
Carbon black satisfying ≦ CATB ≦ 140 is blended in a weight ratio of the former: the latter = 100: 10 to 100, and the total amount of (A) and (B) is the rubber component 10.
The rubber composition is 50 to 70 parts by weight per 0 parts by weight.

The rubber component used in the present invention is not particularly limited and widely known ones can be widely used, for example, natural rubber (NR), polyisoprene rubber (IR), butadiene rubber (BR), styrene-butadiene. Rubber (SB
R), acrylonitrile-butadiene rubber (NBR),
Examples thereof include synthetic rubbers such as ethylene-propylene-diene rubber (EPDM) and modified products thereof. These rubbers may be used alone or in combination of two or more.

In the present specification, CTAB means AST.
Carbon Black 1 determined from the oil absorption of cetyltrimethylammonium bromide in accordance with MD3765
It means a specific surface area (m ² ) per g. 24M4DBP
Means the oil absorption of dibutylphthalate (ml / 100 g) after four compressions at 24000 psi. In addition, N ₂ SA is based on ASTM D3037,
1 g of carbon black obtained from the adsorption amount of nitrogen (N ₂ )
The specific surface area (m ² ) per contact is ASTM15
It means the iodine adsorption amount (g) per 1 kg of carbon black determined according to 10.

The carbon black used as the component (A) in the present invention is 80≤CATB≤110, 65≤24.
It is necessary to satisfy M4DBP ≦ 75 and N ₂ SA / IA ≧ 1.1. Carbon black outside these ranges cannot achieve the object of the present invention. For example, when the CATB is less than 80, the rigidity and tear fracture physical properties of the obtained tire are deteriorated, while the CTAB is 110.
If it is larger than the above range, the heat generation of the obtained tire becomes large, which is inconvenient. Also, 24M4DBP is 6
If it is less than 5, the processability of the rubber composition and the rigidity of the tire to be obtained are reduced, while if 24M4DBP is more than 75, the tear fracture physical properties of the tire to be obtained are decreased and the heat generation property is increased. Is also inappropriate. Furthermore, when N ₂ SA / IA becomes smaller than 1.1,
This is inconvenient because the resulting tire has extremely high heat generation. In the present invention, it is preferable to use, as the component (A), one having 90 ≦ CATB ≦ 100 among the above carbon blacks from the viewpoint of rigidity and heat generation, and further, N ₂ S
It is more preferable to use one having A / IA ≧ 1.15.

The carbon black used as the component (B) in the present invention is required to satisfy 100≤CATB≤140. Carbon black outside these ranges cannot achieve the object of the present invention. For example, if CATB is less than 100, the rigidity of the obtained tire is reduced, while if CTAB is greater than 140, the heat generation of the obtained tire is increased, which is inconvenient. In the present invention, it is preferable to use, as the component (B), one having 70 ≦ 24M4DBP ≦ 100 among the above carbon blacks. When 24M4DBP is less than 70, the rigidity of the obtained tire tends to decrease, while when 24M4DBP is more than 100, the tear fracture physical property of the obtained tire tends to decrease and the heat generation tends to increase. Is also not preferable.

In the present invention, the above components (A) and (B) are blended in a weight ratio of 100 parts by weight of the former (hereinafter simply referred to as "parts") to 10 to 100 parts by weight of the latter. Is required. If the compounding amount of the latter is less than the above, the rigidity of the obtained tire is lowered, while if the compounding amount of the latter is more than the above, the heat buildup of the obtained tire becomes large, which is inconvenient. In the present invention, the former component (A) and the component (B) are used in a weight ratio of the former 10
It is preferable to mix the latter in a ratio of 30 to 70 parts per 0 part.

In the present invention, the carbon black obtained by mixing the component (A) and the component (B) in the above proportion is used as the rubber component 1.
It is important to mix 50 to 70 parts per 00 parts.
If the amount of mixed carbon black is less than 50 parts,
On the other hand, if the compounding amount of the mixed carbon black is more than 70 parts, the resulting tire will have low tear-rupture properties and high heat generation property. is there. In the present invention, it is desirable to add 55 to 65 parts of the mixed carbon black per 100 parts of the rubber component.

The composition of the present invention preferably contains sulfur as a vulcanizing agent in an amount of about 3 to 10 parts per 100 parts of the rubber component. If the blending amount of sulfur is too small, the adhesion with the steel cord tends to decrease, and conversely, if it is too large, the heat generated during tire running tends to cause thermal deterioration and the property of tear fracture tends to deteriorate. In any case, it is not preferable.

In the composition of the present invention, in addition to the above-mentioned components, known vulcanization accelerators, vulcanization acceleration aids, vulcanization retarders, organic peroxides, reinforcing agents, fillers, softening agents, plasticizers, Antiaging agents, tackifiers, colorants and the like can be added as appropriate.

The rubber composition of the present invention can be easily produced by kneading the above-mentioned components using a conventional processing device such as a roll, a Banbury mixer or a kneader.

[0018]

EXAMPLES The present invention will be further clarified with reference to the following examples.

Examples 1 to 8 and Comparative Examples 1 to 12 The carbon black shown in Table 1 was used as the component (A). Carbon black that meets the requirements of the present invention is A-
1, A-2 and A-3. The carbon black shown in Table 2 was used as the component (B). A carbon black that meets the requirements of the invention is B-1.

[0020]

[Table 1]

[0021]

[Table 2]

Natural rubber 100 parts, sulfur 5 parts, zinc flower 10
Parts, antioxidants (paraphenylenediamine type) 1 part, vulcanization accelerator (sulfenamide type) 1 part, cobalt stearate 2 parts, resorcin 1 part and hexamethylene tetramine 1 part. The components (A) and (B) having the formulations shown below were added and uniformly kneaded with a roll to obtain a rubber composition.

Each rubber composition obtained was vulcanized at 145 ° C. for 50 minutes to obtain a dynamic modulus (E ', MPa), a loss tangent (tan δ), and a physical property for tear fracture (JIS K 63).
01) and the adhesiveness were investigated. Dynamic modulus and tan
δ was measured using a viscoelasticity spectrometer (initial strain 15%, amplitude 1%, frequency 50 Hz, temperature 30 ° C.) manufactured by Iwamoto Seisakusho. The numerical value of the dynamic modulus indicates that the larger the numerical value is, the more excellent the rigidity is, and it is judged that the numerical value of 25 or more is sufficient in terms of the rigidity. The numerical value of tan δ indicates that the smaller the numerical value is, the more excellent the heat resistance is, and a numerical value of 0.23 or less was judged to be sufficient in terms of the heat resistance. Tear fracture property is JIS K 630
According to No. 1, it was investigated using a type A dumbbell. The larger the value is, the better the tear fracture property is.
A numerical value of 20 or more was judged to be sufficient in terms of tear fracture physical properties. The adhesive force is expressed by indexing the pulling force measured by the pulling test method using a steel cord for tire. The larger the value is, the better the adhesion with the steel cord is, and the value of 110 or more was judged to be sufficient in terms of the adhesion with the steel cord.

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

[Table 5]

The following is clear from Tables 3-5.
That is, when the rubber composition of the present invention is used, it is possible to obtain an excellent tire having high rigidity, low heat buildup, high tear fracture physical properties, and good adhesion to steel cords. Comparative Example 1 is an example in which the component (B) is not mixed, but it is insufficient in terms of rigidity. Comparative Example 2 is an example in which carbon black having a CATB of more than 110 is used as the component (A), but it is insufficient in terms of heat generation. Comparative Example 3 is an example in which carbon black having a CATB of less than 80 is used as the component (A), but it is insufficient in terms of rigidity, physical properties for tear fracture and adhesiveness with a steel cord.
Comparative Example 4 is an example in which carbon black having 24M4DBP exceeding 75 is used as the component (A), but it is insufficient in terms of heat generation property and tear fracture physical property. Comparative Example 5
This is an example of using carbon black having a 24M4DBP of less than 65 as the component (A), but it is insufficient in terms of rigidity and adhesiveness with a steel cord. Comparative Example 6
This is an example of using carbon black having N ₂ SA / IA less than 1.1 as the component (A), but it is insufficient in terms of heat generation. In Comparative Example 7, CATB is 1 as the component (B).
It is an example using more than 40 carbon black,
Insufficient heat generation. Comparative Example 8 is an example in which carbon black having a CATB of less than 100 is used as the component (B), but it is insufficient in terms of rigidity and adhesiveness with a steel cord. Comparative Example 9 is an example in which the blending ratio of the component (B) to the component (A) is small, but the rigidity and the adhesiveness to the steel cord are insufficient. Comparative Example 10 is an example in which the mixing ratio of the component (B) to the component (A) is large, but it is insufficient in terms of heat generation. Comparative Example 11 is an example in which the blending amounts of the component (A) and the component (B) with respect to the rubber component are small, but it is insufficient in terms of rigidity and adhesiveness with the steel cord. Comparative Example 12
Is an example in the case where the compounding amounts of the component (A) and the component (B) with respect to the rubber component are small, but it is insufficient in terms of exothermic property and tear fracture physical property.

[0028]

Industrial Applicability According to the present invention, there is provided a rubber composition capable of enhancing only rigidity without deteriorating properties such as low exothermic property, high tear fracture property, and adhesiveness with steel cord.

Claims (1)

[Claims] 1. (A) 80 ≦ CATB ≦ 110, 65 ≦
Carbon black satisfying 24M4DBP ≦ 75 and N ₂ SA / IA ≧ 1.1, and (B) 100 ≦ CATB ≦ 1
Carbon black satisfying 40 is blended in a weight ratio of former: latter = 100: 10 to 100, and the total amount of (A) and (B) is 5 per 100 parts by weight of the rubber component.
A rubber composition comprising 0 to 70 parts by weight.