JPH0336849B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a rubber composition for use in the tread of competition tires, particularly for running on circuits, which has small temperature changes in skid characteristics (road surface gripping force) and excellent blowout resistance. . [Prior Art] Conventionally, rubber compositions for competition tire treads include:
SAFN-110 (ASTM
) or iodine adsorption amount 160 to 200 as shown in Japanese Patent Application Laid-Open No. 1734-1982.
mg/g, DBP oil absorption of 110 to 140 ml/100 g, and specific coloring power (IRB #3 as 100) of 120 to 150. Carbon black with a smaller particle size than SAF was blended. However, it has not been sufficient to balance wear resistance, skid characteristics, and blowout resistance characteristics at a high level that is sufficiently satisfactory for each competition. Therefore, the present inventors conducted intensive studies on carbon black, and found that the nitrogen specific surface area was
^200-500m2 /g, DBP oil absorption of 90ml/100g or more, specific tinting power (Tint value) of 120-150, volatile content
By using carbon black for pigments with a content of 6.0% or less, it was possible to obtain a rubber composition with low temperature dependence of skid properties, excellent abrasion resistance, and nearly satisfactory blowout resistance. However, this rubber composition may still be insufficient in terms of blowout resistance and maneuverability when the weight or speed of the competition vehicle increases and becomes highly severe. In the case of increasing the amount, the blowout resistance was insufficient. [Object of the Invention] The present invention provides a tire suitable for use in treading of competition tires, which exhibits small temperature changes in skid characteristics without impairing blowout resistance and maneuverability under high severity conditions, and has excellent wear resistance. The purpose of the present invention is to provide a rubber composition with a high quality. [Structure of the Invention] Therefore, the present invention comprises blending 120 parts by weight or more of carbon black with 100 parts by weight of raw material rubber consisting of at least one type of diene rubber,
(1) Carbon black for pigments with a nitrogen specific surface area of 200 to 500 m ² /g, a DBP oil absorption of 90 ml/100 g or more, a specific coloring power of 120 to 150, and a volatile content of 6.0 or less is 10 to 60 of all carbon blacks. %, and (2) nitrogen specific surface area is 80 to 180 m ² /g, DBP oil absorption is 100
The object of the present invention is to provide a rubber composition for tire treads, characterized in that the remaining carbon black is carbon black for rubber having an amount of ml/100 g or more. Hereinafter, the configuration of the present invention will be explained in detail. The diene rubber used in the present invention is, for example, styrene-butadiene copolymer rubber,
These include styrene-butadiene copolymer rubber with a high styrene content of 30% or more, butadiene rubber, synthetic isoprene rubber, natural rubber, butyl rubber, halogenated butyryl rubber, etc. In the present invention, at least one of these diene rubbers, ie, one or a blend thereof, is used as the raw material rubber. The pigment carbon black used in the present invention has a nitrogen specific surface area (N ₂ SA) of 200 to 500 m ² /g, preferably 250 to 450 m ² /g, and a DBP oil absorption of 90 m 2 /g.
ml/100g or more, preferably 110ml/100g or more, a specific tinting power (Tint value) of 120 to 150, and a volatile content of 0.6% or less, preferably 3.0% or less. If N ₂ SA is less than 200 m ² /g, it is not possible to expect a significant improvement in wear resistance compared to the use of carbon black for rubber. Furthermore, when N ₂ SA exceeds 500 m ² /g, dispersion becomes poor in the usual mixing method with raw rubber, and wear resistance also deteriorates. DBP oil absorption is a particularly important property for carbon black for pigments. By increasing the oil absorption of DBP, it is possible to improve the dispersibility of carbon black for pigments with very fine particle size, and at the same time improve tensile strength and Abrasion resistance can be improved. If the DBP oil absorption amount is less than 90ml/100g, not only will the dispersibility deteriorate, but the abrasion resistance will also decrease, and the advantage of using carbon black for pigments will disappear. Furthermore, if the Tint value is less than 120, no improvement in wear resistance can be expected, and if it exceeds 150, a decrease in dispersibility will result. Volatile content is not a very important characteristic in ordinary carbon black for rubber, but it is extremely important in the present invention. In other words, when carbon black is used as a pigment, it must have a high volatile content in terms of compatibility with resins.
That is, carbon black with a high degree of oxidation is preferred. In other words, the volatile content is a measure of the degree of oxidation of carbon black. When such carbon black for pigments is blended with rubber, carbon black with a high volatile content, that is, a high degree of oxidation, not only delays vulcanization but also has low surface activity, resulting in low breaking strength and durability. Abrasion resistance is also reduced. Therefore, it is preferable that the volatile content is 6.0% or less and as low as possible. If the volatile content exceeds 6.0%, not only will vulcanization be delayed as described above, but the tensile strength and abrasion resistance will also decrease, eliminating the merits of using carbon black for pigments. Furthermore, the carbon black for rubber used in the present invention has an N ₂ SA of 80 to 180 m ² /g and a DBP oil absorption of 100 ml/g.
It is 100g or more. If the N ₂ SA is less than 80 m ² /g, the absolute level of skid properties will decrease, which is undesirable, and if the DBP oil absorption is less than 100 ml/100 g, no improvement in blowout resistance can be expected. In the present invention, 120 parts by weight or more of carbon black is blended with 100 parts by weight of the raw material rubber. This is because if the amount is less than 120 parts by weight, the wear resistance and skid properties will be insufficient. and,
In the present invention, the pigment-use carbon black accounts for 10 to 60% of this carbon black. If the carbon black for pigments is less than 10% of the total carbon black content, there is no effect of reducing the temperature change in skid properties (preferably 20% or more). In addition, if the carbon black for pigments exceeds 60%,
No improvement in blowout resistance can be expected. The remaining carbon blacks other than the carbon black for pigments are the above-mentioned carbon blacks for rubber. This is to avoid impairing blowout resistance. Furthermore, the rubber composition of the present invention can also contain compounding agents commonly used in the rubber industry, such as a vulcanizing agent, a vulcanization accelerator, zinc white, stearic acid, an anti-aging agent, and oil. Examples and comparative examples are shown below. Examples and Comparative Examples Raw rubber and compounding agents other than the vulcanization accelerator and sulfur were mixed for 4 minutes using a Kobe Steel B-type Banbury mixer (capacity 1.8).
The vulcanization accelerator and sulfur were kneaded for 4 minutes using an 8-inch roll to obtain a rubber composition having the formulation contents (parts by weight) shown in Table 1 below. The basic properties of the carbon black used are shown in Table 2 below. Table 1 SBR ⁽¹⁾ 137.50 parts by weight Zinc white 5.00 parts by weight Stearic acid 2.00 parts by weight Antioxidant A ⁽²⁾ 2.00 parts by weight Antioxidant B ⁽³⁾ 2.00 parts by weight Carbon black total 165.00 parts by weight Aroma oil 100.00 parts by weight Naphthene oil 50.00 parts by weight Accelerator A ⁽⁴⁾ 1.80 parts by weight Accelerator B ⁽⁵⁾ 0.30 parts by weight Accelerator C ⁽⁶⁾ 0.10 parts by weight Sulfur 2.30 parts by weight Note: (1) 35% styrene content Styrene-butadiene copolymer Combined rubber, oil extension amount 37.50 parts by weight. (2) N-phenyl-N'-isopropyl-p-phenylenediamine. (3) Polymerized 2,2,4-trimethyl-
1,2-dihydroquinoline. (4) N-cyclohexyl-2-benzothiazolyl-sulfenamide. (5) 1,3-diphenylguanidine. (6) Tetramethylthiuram disulfide.

【table】

[Table] Next, this rubber composition was press-vulcanized at 160° C. for 25 minutes using a vulcanization press specified in JIS K6301, and the physical properties of the vulcanized product were evaluated. The results are shown in Table 3 below. The method for measuring the physical properties of each vulcanizate is as follows. SN: Values measured on a wet 3M Safety Walk road surface using a British Stanley portable skid tester were measured using Carbon Black B (traditionally used in cap tread rubber for competition tires). The value of SAF, which is the highest grade of carbon black for rubber, is expressed as an index of 100. tanδ: Using a viscoelastic spectrometer made by Iwamoto Seisakusho, elongation deformation with an initial strain of 10% and a dynamic strain of 2%, and frequency.
Measured under the condition of 20Hz. Blow Out Time: Using a Gutstritz type flexometer, load 7 kg, stroke 4.44 mm, frequency 1800 r.pm,
Measurements were made under the condition of an ambient temperature of 100°C, and the time until blowout occurred was measured.

〔Effect of the invention〕

As explained above, according to the present invention, by blending a certain amount of a certain specific carbon black with the carbon black for pigments, the skid property can be improved by using the carbon black for pigments. While maintaining the advantage of reducing the temperature dependence of hysteresis loss, it is possible to suppress the decrease in blowout resistance that occurs when a large amount of pigment carbon black is used, making it a rubber composition suitable for the tread of competition tires. Obtainable.

Claims (1)

[Claims] 1. 120 parts by weight of carbon black for 100 parts by weight of raw material rubber consisting of at least one type of diene rubber.
(1) Nitrogen specific surface area is 200
~500m ² /g, DBP oil absorption 90ml/100g or more,
Carbon black for pigments with a specific coloring strength of 120 to 150 and a volatile content of 6.0 or less ranks 10th of all carbon blacks.
~60%, and (2) nitrogen specific surface area is 80~180
^1. A rubber composition for a tire tread, characterized in that the remaining carbon black is carbon black for rubber having an oil absorption amount of 100 ml/100 g or more in DBP.