JPH1017719A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for a tire tread, having low heat generation and good abrasion resistance at the same time. SOLUTION: This composition is composed of 100 pts.wt. of a rubber component and 30-60 pts.wt. of carbon black, which has properties of a CTBA absorption specific surface area of >=140m<2> /g, a DBP oil absorption of >=140ml/100g, a CDBP oil absorption of >=115ml/100g, TINT of >=140%, ΔD50 of <=50nm and a nitrogen absorption specific surface area of >=150m<2> /g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a rubber composition for a tire tread.

[0002]

2. Description of the Related Art Conventionally, treads of tires used for trucks and buses are required to have considerably high abrasion resistance. Therefore, rubber black as a raw material has been blended with carbon black having high reinforcement of ISAF class. . In recent years, the market demand for the improvement of abrasion resistance has been more and more increased. In order to improve the abrasion resistance performance, an increase in the amount of compounded carbon black and the use of SAF class carbon black have been performed.

[0003]

However, there is a limit to the improvement of the wear resistance by increasing the amount of the compounded carbon black. When the limit is exceeded, the effect of the improvement of the wear resistance is reduced, and the tire tread is reduced. The amount of heat generated during use is increased, and the heat generation is significantly deteriorated.

[0004] The use of SAF class carbon black is expected to improve the abrasion resistance. In this case, however, the particle size of the carbon black is reduced, and the dispersibility of the carbon black in the compounded rubber is reduced. Decreases,
Not only does not exhibit the expected effect of improving the wear resistance, but also the heat generation during use of the tire tread deteriorates.
Therefore, an object of the present invention is to provide a rubber composition for a tire tread which solves the above-mentioned problems associated with improvement in wear resistance and has improved wear resistance without deterioration of heat generation performance.

[0005]

Means for Solving the Problems In general, the basic characteristics of carbon black include the particle size and the size of agglomerates of the particles. The smaller the particle size, the more the reinforcing property and the wear resistance are improved. On the other hand, it is known that the above problems, that is, deterioration of heat buildup and deterioration of dispersibility are involved. On the other hand, it is known that abrasion resistance can be improved by increasing the size of the aggregate of carbon black particles (JP-A-5-25325, JP-A-6-279).
624).

[0006] Among these basic characteristics, the present inventors:
Focusing on improving the dispersibility by increasing the size of the aggregate, in addition to these conventional basic characteristics, blending a specific amount of carbon black whose distribution and size of the aggregate diameter are within a specific range It was confirmed through experiments that the above problems could be solved at once, and the present invention was completed.

That is, the rubber composition for a tire tread according to the present invention has a rubber component of 100 parts by weight, a CTAB adsorption specific surface area of 140 m ² / g or more, and a DBP oil absorption of 140 ml.
/ 100g or more, CDBP oil absorption is 115ml / 100g
As described above, 30 to 60 parts by weight of carbon black having a TINT of 140% or more, a ΔD50 of 50 nm or less, and a nitrogen adsorption specific surface area of 150 m ² / g or more.

[0008] Among the characteristics of the carbon black, CT
AB adsorption specific surface area is 140-200 m ² / g, DBP oil absorption is 140-160 ml / 100 g, CDBP oil absorption is 115-150 ml / 100 g, and TINT is 14
0-180%, the ΔD50 is 25～45Nm, the nitrogen adsorption specific surface area is preferably 150~180m ² / g.

Preferably, the rubber component contains at least natural rubber. It is preferable to further include sulfur and a vulcanization accelerator having the same weight or more as the sulfur. The rubber composition for a tire tread of the present invention is preferably used for a tire tread of a heavy-duty vehicle.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition for a tire tread of the present invention contains a rubber component and carbon black.
Hereinafter, the rubber composition for a tire tread will be described in detail. [Rubber component] The rubber component contained in the rubber composition for a tire tread of the present invention is not particularly limited, and may be, for example, any one of a natural rubber, a diene-based synthetic rubber alone, or a combination thereof. When this composition is used for a tire tread of a heavy-duty vehicle, it is preferable that the rubber component contains at least natural rubber. The diene-based synthetic rubber is not particularly limited, for example,
Examples include isoprene rubber (IR), butadiene rubber (BR), and styrene butadiene rubber (SBR), and one or more kinds can be used.

[Carbon Black] The carbon black contained in the rubber composition for a tire tread of the present invention has physical properties such as nitrogen adsorption specific surface area, DBP oil absorption, CDBP oil absorption, TINT, ΔD50 and CTAB adsorption specific surface area. The type is not particularly limited as long as it is listed below.

As carbon black, for example, S
Carbon black having a structure higher than that of a normal product such as an AF class is preferable, and one or two or more carbon blacks can be used. Hereinafter, the physical properties of carbon black will be described. Nitrogen adsorption specific surface area of carbon black (N ₂
SA) indicates the size of the particle diameter. When the specific surface area is large, the particle size is small. The nitrogen adsorption specific surface area is not particularly limited as long as it is 150 m ² / g or more.
It is preferably 80 m ² / g. At less than 150 m ² / g,
The effect of improving the wear resistance is not sufficient. Also, 180m ² / g
When it exceeds, the dispersibility is improved by increasing the size of the aggregate, but there is a limit.

The DBP oil absorption of carbon black is an index of the size of the structure, and is 140 ml / 100 g.
There is no particular limitation as long as it is above, preferably 140 to 16
0 ml / 100 g, more preferably 145 to 155
ml / 100 g. If it is less than 140 ml / 100 g, the size of the aggregate is too small, so that the abrasion resistance cannot be improved or the dispersibility cannot be sufficiently obtained. If it exceeds 160 ml / 100 g, workability may be reduced.

The CDBP oil absorption of carbon black is an indicator of the strength of the structure, and is 115 ml / 100 g.
There is no particular limitation as long as it is above, and preferably 115 to 15
0 ml / 100 g, more preferably 120-140
ml / 100 g. If the amount is less than 115 ml / 100 g, a predetermined effect is hardly obtained because the aggregate of carbon black is easily broken by shearing during kneading or the like. 150ml / 10
If it exceeds 0 g, workability may be reduced.

TINT (coloring power) of carbon black
Is one factor for imparting high abrasion to the rubber component, and is not particularly limited as long as it is 140% or more, preferably 140 to 180%, more preferably 15 to 180%.
0 to 180%. If it is less than 140%, the abrasion resistance cannot be sufficiently improved. If it exceeds 180%, there is a problem in production, it is difficult to satisfy other requirements, and production may not be possible substantially.

The distribution of the aggregate diameter of carbon black is preferably sharp. Therefore, ΔD50 of carbon black is not particularly limited as long as it is 50 nm or less,
It is preferably from 25 to 45 nm, more preferably from 30 to 45 nm.
40 nm. If ΔD50 is less than 25 nm, the exothermicity is greatly deteriorated. If ΔD50 exceeds 50 nm, the abrasion resistance is not sufficiently improved. The maximum frequency Stokes diameter (Dst) of the carbon black is preferably 70 nm or less. If the Stokes diameter exceeds 70 nm, satisfactory wear resistance cannot be obtained.

The surface of carbon black has pores of about several angstroms, and rubber cannot enter these pores. Therefore, the evaluation of the specific surface area to the extent that rubber can penetrate is expressed by the degree of adsorption of CTAB (cesyltrimethylammonium bromide), which is a large adsorbed molecule.
This CTAB value (CTAB adsorption specific surface area) is 140 m ^2.
/ g or more is not particularly limited, preferably 140 to 2
00 m ² / g, more preferably 150 to 180 m ² / g. If it is less than 140 m ² / g, the improvement in wear resistance is not sufficient. If it exceeds 200 m ² / g, low heat build-up and workability may be significantly deteriorated.

The iodine adsorption amount of carbon black is 145
175 mg / g, more preferably 145-175 mg / g. If the amount is less than 145 mg / g, the effect of improving the abrasion resistance is not sufficient. If the amount exceeds 175 mg / g, the size of the carbon black aggregates is increased to improve the dispersibility, but there is a limit. (Rubber composition for tire tread) The rubber composition for tire tread of the present invention contains a rubber component and carbon black, and the compounding amount of the rubber component and carbon black is:
Carbon black 30 per 100 parts by weight of rubber component
It is in the range of ６０60 parts by weight, preferably in the range of 35〜55 parts by weight. If the compounding amount of the carbon black is less than 30 parts by weight, sufficient wear resistance cannot be obtained even if the carbon black having the above-mentioned properties is used. If the amount is more than 60 parts by weight, the workability is reduced, the effect of improving the wear resistance is reduced, and the heat generation during use of the tire tread is increased.

The rubber composition for a tire tread of the present invention comprises:
When sulfur and a vulcanization accelerator having the same weight or more as the sulfur are further contained, monosulfide bonds which are strong in heat fatigue resistance and hardly cause a change in physical properties are increased, and therefore, in heavy load tires which are particularly strict in use conditions, this vulcanization accelerator is used. A sulfur system is preferred.
The rubber composition for a tire tread of the present invention may contain one or more fillers such as silica, calcium carbonate, and clay, and one or more additives such as a silane coupling agent, if necessary.

The method for producing the rubber composition for a tire tread of the present invention is not particularly limited, and a known method can be applied. Specifically, for example, using a kneading machine such as a Banbury mixer, the base chemicals such as filler, plasticizer, vulcanization aid, and antioxidant are 100 to 160.
C., kneaded with rubber component and carbon black for 4 to 6 minutes, discharged, added with final chemicals such as sulfur and vulcanization accelerator, and kneaded at 80 to 100.degree. C. for 2 to 3 Can be.

The rubber composition for a tire tread thus obtained can be formed into a tire tread by molding and vulcanizing. The rubber composition for a tire tread of the present invention does not contain a large amount of a filler such as carbon black as a reinforcing agent, but rather has a small amount, so that the rubber has good elongation and is obtained from this rubber composition. The tire tread has good followability even on a rough road where large deformation of the tire tread occurs, and rubber chipping hardly occurs. Therefore, it is excellent in durability even when used for tires for rough roads.

The tire tread obtained from the rubber composition of the present invention has a low heat build-up and thus has a good heat build-up, is suitable for high-speed running on a highway, and can store heat even if it is thicker than a conventional tread. , And can run on the same level as a normal tread, resulting in a tire with a longer life. The tire tread obtained from the rubber composition of the present invention is excellent in abrasion resistance and can be made thinner.Thus, it is possible to reduce the weight of the tire while maintaining the same life, and Fuel efficiency.

Normally, when a large amount of highly reinforcing carbon black is used, it is expected that the Mooney viscosity, which is an index of workability in the manufacturing process, will be significantly increased and workability will be deteriorated. Has a unique aggregate structure, so that an increase in Mooney viscosity is suppressed.

[0024]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples. (Examples 1-2 and Comparative Examples 1-2) A rubber composition for a tire tread having the composition shown in Table 1 below was produced by the following method. Using a Banbury mixer, fillers, plasticizers, vulcanization aids and antioxidants were added as base chemicals to 150
After kneading with carbon black and a rubber component at 4 ° C. for 4 minutes, the mixture is discharged, and sulfur and a vulcanization accelerator as final chemicals can be kneaded at 90 ° C. for 2 minutes.

The rubber composition for a tire tread obtained is
It was evaluated by vulcanization at 150 ° C for 40 minutes at 80 kgf.

[0026]

[Table 1]

Butadiene rubber: BR manufactured by Nippon Synthetic Rubber Co., Ltd.
10 Anti-aging agent: N-isopropyl-N'-phenyl-p-
Phenylenediamine (Sumitomo Chemical Co., Antigen 3
C). Stearic acid: manufactured by NOF Corporation. Zinc flower: manufactured by Mitsui Kinzoku.

Sulfur: manufactured by Tsurumi Chemical Company. Vulcanization accelerator: N-tert-butyl-2-benzothiazylsulfamide (Ouchi Shinko, Noxeller NS). Carbon black: Type A: carbon black according to the present invention.

Type B: SAF carbon (Tokai Carbon, Seast 9). Type C: ISAF carbon (Tokai Carbon, Seast 6). The properties of these carbon blacks are as shown in Table 2 below.

[0030]

[Table 2]

The properties of the carbon black were measured by the following methods. Nitrogen adsorption specific surface area: A method based on ASTM D3037-88. DBP oil absorption: A method based on JIS K6221-1982. CDBP oil absorption: Pulverized according to ASTM D3493, and DBP was determined according to JIS K6221.

TINT: A method based on ASTM D3265-85. Stokes diameter (Dst) at the maximum frequency, ΔD50: The distribution of the aggregate diameter of carbon black was measured by the following method using a centrifugal sedimentation method using a disk centrifuge manufactured by Lebre . About 10mg of carbon black
Accurately weigh and add to a 20% aqueous ethanol solution to which a small amount of surfactant is added, and adjust the carbon black concentration to about 0.02% by weight.
After that, the mixture was dispersed by ultrasonic waves to obtain a sample solution.
Rotation speed of disk centrifuge is 8000 rpm
m, and 14 ml of spin solution (pure water) was added. Thereafter, 1 ml of a buffer solution (20% aqueous ethanol solution) was injected, and centrifugal sedimentation was started all at once. Aggregate diameter distribution curves as shown in FIG. 1 were created by the photoprecipitation method, and the Stokes diameter (Dst) and the half width (ΔD50) were determined.

CTAB adsorption specific surface area: ASTM D37
65-85. Iodine adsorption amount: A method based on ASTM 1510-81. Various physical properties of the tire tread obtained from each of the rubber compositions obtained in the above Examples and Comparative Examples were evaluated by the following methods. Mooney viscosity: ML (1 + 4) was measured at 130 ° C. according to JIS K6299.

Hardness: JIS-A hardness after vulcanization was measured at 20 ° C. E ^* : Viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., E ^* , tan δ at 70 ° C., 10 Hz, 0.2% strain.
Was measured. Lambourn: The wear of the test piece was measured using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho under the conditions of a load of 5 kg and a slip ratio of 60%. The wear resistance is better as the index is larger, with the value of Example 1 being 100.

The evaluation results are shown in Table 3 below.

[0036]

[Table 3]

As shown in Table 3, the rubber composition of Example 1 using the carbon black having the physical properties specified in the present invention is different from the rubber composition of Comparative Example 1 using the conventional carbon black. In the tire tread after vulcanization, the hardness is the same, but due to the low heat build-up of carbon black, LC (loss coefficient / loss compliant ice, E ″ / (E ^* ) ² ), which is an index of heat build-up, is reduced. In addition, due to the high reinforcing property of carbon black, the wear index of Lambourn, which is an index of wear resistance, is improved.

The rubber composition of Example 2 has the same level of tan δ as an index of rolling resistance as compared with the rubber composition of Comparative Example 2 using conventional carbon black, but has a Lambourn abrasion index. Is improving. Normally, when a large amount of high reinforcing carbon black is used as in the above examples, it is expected that the Mooney viscosity, which is an index of workability in the manufacturing process, will significantly increase and workability will deteriorate. In the composition, since the carbon black used has a unique aggregate structure, an increase in Mooney viscosity is suppressed.

[0039]

The rubber composition for a tire tread of the present invention can provide a rubber composition for a tire tread having improved abrasion resistance without deteriorating heat generation performance.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of an aggregate diameter distribution curve used for obtaining the maximum frequency Stokes diameter (Dst) and half width (ΔD50) of carbon black.

Claims (5)

[Claims] 1. A rubber component having 100 parts by weight, a CTAB adsorption specific surface area of 140 m ² / g or more, a DBP oil absorption of 140 ml / 100 g or more, and a CDBP oil absorption of 115 ml
/ 100 g or more, TINT is 140% or more, ΔD50 is 50 nm or less, and a carbon composition having a nitrogen adsorption specific surface area of 150 m ² / g or more is 30 to 60 parts by weight. 2. The characteristics of the carbon black,
AB adsorption specific surface area is 140-200 m ² / g, DBP oil absorption is 140-160 ml / 100 g, CDBP oil absorption is 115-150 ml / 100 g, and TINT is 14
0-180%, the ΔD50 is 25～45Nm, the nitrogen adsorption specific surface area for a tire tread rubber composition according to claim 1 which is 150~180m ² / g. 3. The rubber composition for a tire tread according to claim 1, wherein the rubber component contains at least natural rubber. 4. The rubber composition for a tire tread according to claim 1, further comprising sulfur and a vulcanization accelerator having the same weight or more as the sulfur. 5. The rubber composition for a tire tread according to claim 1, which is used for a tire tread of a vehicle for heavy load.