JPH0693136A - Rubber composition for tire tread - Google Patents

Abstract

PURPOSE:To provide a compsn. excellent in grip and abrasion resistance. CONSTITUTION:100 pts.wt. rubber component is compounded with 40-200 pts.wt. carbon black having a CTAB of 140-200m<2>/g, a 24M4 DBP absorption of 106-140ml/100g, a Stokes equivalent diameter Dst of aggregate by centrifugal settling of 75nm or lower, and a ratio of the half-value width DELTADst of aggregate distribution by centrifugal settling to the Dst, namely DELTADst/Dst=0.65-0.85.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a tire tread, and more specifically, it is suitable for a tread of a racing tire having excellent wear resistance and gripping force, especially for circuit running. It relates to a rubber composition.

[0002]

2. Description of the Related Art Conventionally, in order to improve the gripping force (road grasping force) of a rubber composition for tread, styrene-butadiene copolymer rubber (SBR) having a high styrene content and butyl rubber having a high glass transition temperature are used. Often by using a polymer in the rubber composition. Further, a large amount of carbon black having a small particle diameter, that is, a large specific surface area is added to this, or a large amount of high aroma oil is added. However, SAF with the smallest particle size among the carbon blacks normally used for rubber
However, it is difficult to obtain sufficient grip force only by the effect of the small particle size of carbon black, and in order to obtain sufficient grip force, a larger amount of oil must be added. It was

Therefore, although the carbon black having a small particle size, which is said to have good wear resistance, is used, the wear resistance is remarkably lowered and the wear appearance is deteriorated.
There was a problem that the grip power was reduced. Therefore,
In order to improve these problems, JP-A-61-143454 discloses that N2SA is 200 to 500 m ² / g and DBP oil absorption is 91 ml / 1.
The effect of improving the wear resistance when using color carbon black having a weight of 00 g or more, a TINT of 120 to 150, and a volatile content of 6.0% or less is disclosed in Japanese Patent Application Laid-Open No. 03-111455.
A is 180-250 m ² / g, DBP oil absorption is 115-135 ml / 100
g, N2SA / IA 0.90 to 1.50, ΔD50 / D mode
0.67 to 0.81 and ΔDBP, the effect of improving abrasion resistance when using carbon black of 20 ml / 100 g or less is disclosed. However, these levels have not yet reached the level of satisfaction.

As described above, it is extremely difficult to have a high gripping force and excellent wear resistance, and at least in the prior art, a satisfactory rubber composition for tread has not been obtained.

[0005]

DISCLOSURE OF THE INVENTION The present invention is for a tread of an excellent tire having excellent gripping power and good wear resistance, particularly a high performance tire and a racing tire such as a race or rally which requires severe driving conditions. The purpose of the present invention is to provide a rubber composition suitable as.

[0006]

Means for Solving the Problems The tire tread of the present invention
The rubber composition for CTAB is 140-200 m²/ g, 24M4D
BP oil absorption is 106-140ml / 100g, flocculation by centrifugal sedimentation method
Body Stokes equivalent diameter D _stIs less than 75 nm, and this D_stWhen
Full width at half maximum ΔD of aggregate distribution measured by centrifugal sedimentation method_St
Ratio to ΔD_St/ D_stCarbon black with a value of 0.65 to 0.85
40 to 200 parts by weight for 100 parts by weight of the rubber component.
It is characterized by being combined. Where CTAB is
It represents the effective specific surface area of the
It is an index different from N2SA (nitrogen specific surface area). N
2SA is a pore that does not participate in rubber on the surface of carbon black
Not only the measured value, but the same depending on the manufacturing method
The smaller the particle size of carbon black, the smaller the CTA
It is known to be significantly different from B.

The inventors of the present invention have confirmed that CTAB is effective as an index of rubber-carbon black interaction, particularly in carbon black having a small particle size. The higher this value, the higher the abrasion resistance and the grip force. We have confirmed that it will improve. Further, it was confirmed that the 24M4DBP oil absorption (compressed dibutyl phthalate oil absorption) is required to be high in order to show the degree of development of the primary structure and improve the wear resistance. It was also confirmed that the abrasion resistance and the grip force were further improved by sharpening the aggregate distribution, that is, by making D _st as small as possible and keeping ΔD _St / D _st within a certain range. The present invention has been made based on such findings.

The structure of the present invention will be described in detail below. The carbon black used in the present invention is, for example, a furnace type carbon black having the following characteristics. That is, CTAB is 140 to 200 m ² / g, preferably 160 to 1
95m ² / g, 24M4DBP oil absorption is 106 ~ 140ml / 100
g, preferably 110 to 130 ml / 100 g, and D _st of 75 nm
Hereinafter, ΔD _St / D _st is 0.65 to 0.85.

If CTAB is less than 140 m ² / g, it is not possible to expect a great improvement in wear resistance and grip strength as compared with the use of ordinary carbon black. Also, CT
When AB exceeds 200 m ² / g, the dispersibility becomes poor in the usual mixing method with the rubber component, and the abrasion resistance also deteriorates. 24M4DBP oil absorption is an especially important characteristic for carbon black. By increasing 24M4DBP oil absorption, it is possible to improve the dispersibility of carbon black with a very small particle size, while at the same time improve tensile strength and wear resistance. Can be increased. If the 24M4DBP oil absorption is less than 106 ml / 100g, not only the dispersibility deteriorates, but also the abrasion resistance decreases. When it exceeds 140 ml / 100 g, the kneading property is remarkably reduced.

D _st is the maximum frequency of Stokes 'equivalent diameter (nm) in the aggregate Stokes' equivalent diameter distribution obtained by the centrifugal sedimentation method. If this value is larger than 75 nm, both wear resistance and gripping power deteriorate. Further, the ratio ΔD _St / D of this D _st to the full width at half maximum ΔD _St of the aggregate distribution measured by the centrifugal sedimentation method
_{If st} is less than 0.65, it is difficult to produce carbon black, whereas if _st is more than 0.85, both abrasion resistance and grip strength are deteriorated. Incidentally, the centrifugal sedimentation method here is a method of measuring an aggregate distribution using a disc centrifuge manufactured by Joyce-Rable, which utilizes the fact that particles having a larger Stokes diameter diffuse faster. The method is to obtain the size of the sedimented particles.

Examples of the rubber component used in the present invention include ordinary diene rubbers such as styrene-butadiene copolymer rubber and styrene content of 30.
At least 1% by weight of a high styrene content styrene-butadiene copolymer rubber, butadiene rubber, synthetic isoprene rubber, natural rubber, butyl rubber, halogenated butyl rubber, etc., or a blend thereof is included, preferably a high styrene content styrene-butadiene copolymerization. A rubber or a blend of this copolymer rubber and another rubber.

In the present invention, the above carbon black is blended with the rubber component. The compounding amount of this carbon black may be a compounding amount usually adopted in the case of carbon black for rubber, for example, in the case of a rubber composition for a tread of a high performance tire traveling on a general road, 100 parts by weight of the rubber component is added. On the other hand, it is 40 to 90 parts by weight of carbon black, and in the case of the rubber composition for tire tread for competition, it is used in 90 to 200 parts by weight per 100 parts by weight of the rubber component. Further, the above-mentioned carbon black and carbon black for general rubber may be blended and used, and the blending amount of carbon black in this blend is the same as in the case of independent use, but the carbon black of the present invention Is preferably blended in an amount of 40 parts by weight or more. Further, the rubber composition of the present invention may be compounded with compounding agents used in ordinary rubber industry, that is, vulcanization accelerator, zinc white, stearic acid, antioxidant, oil and the like.

[0013]

Example A rubber composition was prepared according to the formulation content (parts by weight) shown in Table 1. In this case, among the rubber components and compounding agents, the vulcanization accelerator TBBS and the rubber components and compounding agents other than sulfur were used as the B type Banbury mixer (1.
8 L) was mixed for 5 minutes, and then a vulcanization accelerator and sulfur were kneaded with this mixture for 4 minutes with an 8-inch test kneading roll machine to obtain a rubber composition. Table 2 shows the measurement results of the types and characteristics of the carbon black used. The method for measuring the carbon black characteristics is as follows. CTAB : According to ASTM-D3765-80. 24M4DBP oil absorption : According to ASTM D-3493. D _st , ΔD _St : A dry carbon black sample was mixed with a 20% by volume aqueous ethanol solution containing a small amount of a surfactant to prepare a dispersion having a carbon black concentration of 5 mg / 100 cc, which was sufficiently dispersed by ultrasonic waves. Use as a sample. A disk centrifuge unit (made by Joice Loebl, UK) is operated at 8000 rpm.
Set the rotation speed to 10 ml of spin solution (distilled water), and then inject 0.5 ml of buffer solution (aqueous ethanol solution). Then, 0.5 ml of the sample solution is added with a syringe to start centrifugal sedimentation, and at the same time, the recorder is operated to optically create a distribution curve of the aggregate Stokes equivalent diameter. The maximum frequency of Stokes equivalent diameter in the obtained distribution curve is defined as D _st (nm). Further, the aggregate distribution value at 1/2 of the most frequent frequency is defined as the full width at half maximum (ΔD _St ).

The obtained rubber composition was press-vulcanized at 160 ° C. for 20 minutes using a vulcanizing press specified in JIS K6301, and the physical properties of the vulcanized product were evaluated. The results are shown in Table 3. The methods for measuring the physical properties of vulcanized products are as follows. Tensile strength, elongation, 300% tensile stress : According to JIS K6301. Abrasion resistance : 4 minutes under the conditions of load 5kg, slip rate 25%, grindstone GC-80-K, test piece speed 80m / min, sand drop 15g / min using a Lambourn abrasion tester manufactured by Kamijima Seisakusho. The wear loss after running was measured and expressed as (SAF wear amount) × 100 / (sample wear amount). The larger the value, the better the wear resistance,
The appearance of wear is also improved.

Tan δ : Using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho, elongation deformation strain rate 10 ± 2%, frequency, 20 Hz
It was measured under the conditions. tan δ is a measure of grip strength, and the larger the value of tan δ, the larger the grip strength. Table 1 Rubber and compounding agent parts by weight SBR 1712 ^{* 1} 137.5 Lead phosphite ^{* 2} 3.0 Stearic acid 1.0 Aroma oil ^{* 3} 2.5 Carbon black 80.0 Vulcanization accelerator TBBS ^{* 4} 1.38 Sulfur yellow 1.75 Note) * 1 Nippon Zeon Nipol 1712 ( Styrene content 23.5
%).

* 2 Zinhua No. 3 manufactured by Shodo Kagaku. * 3 Kyoseki Process X-140. * 4 N-t-butyl-2-benzothiazolylsulfenamide, Santocure NS manufactured by Monsanto.

[0017]

[0018] In Table 3, Comparative Rubber Composition 1 is the highest grade in carbon black for rubber, that is, when SAF having the largest specific surface area is used, Comparative Rubber Composition 2 is SAF.
When a carbon black having a high 24M4DBP in the grade is used, the comparative rubber composition 3 has a normal 24M4DBP value and CT
The case where carbon black with high AB is used is shown. This is the case where the rubber compositions 1 and 2 of the present invention use the carbon black corresponding to the present invention.

As is clear from the measured values in Table 3,
The rubber compositions 1 and 2 of the present invention are significantly improved in the balance between grip strength and wear resistance as compared with the comparative rubber composition 1 and the comparative rubber compositions 2 and 3 using ordinary carbon black. Recognize.

[0020]

As described above, the rubber composition for a tire tread of the present invention has a CTAB of 140 to 200 m ² / g, 24M.
4DBP oil absorption is 106-140ml / 100g, D _st is 75nm or less,
By blending carbon black having ΔD _St / D _st of 0.65 to 0.85 with the rubber component, the grip strength is excellent, and even if a large amount of oil is blended, the wear resistance is not deteriorated and the wear appearance is good. Therefore, the rubber composition of the present invention,
It is suitable as a tread for high performance tires or competition tires.

Claims (1)

[Claims] 1. CTAB is 140 to 200 m ² / g, 24M4DB
P oil absorption is 106-140 ml / 100g, aggregate Stokes equivalent diameter D _st by centrifugal sedimentation method is 75 nm or less, and ratio of this D _st and full width at half maximum ΔD _St of aggregate aggregate measured by centrifugal sedimentation method ΔD _St A rubber composition for a tire tread, which comprises 40 to 200 parts by weight of carbon black having a / D _st of 0.65 to 0.85 with respect to 100 parts by weight of a rubber component.