JP2003165871A - Rubber composition for tire and tire using the rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To considerably improve weather resistance and discoloration resistance of a tire for a long period. <P>SOLUTION: This rubber composition for the tire comprises 100 pts.wt. rubber component, 10-100 pts.wt. carbon black having 20-150 m<SP>2</SP>/g specific surface area measured by nitrogen adsorption, 5-20 pts.wt. titanium oxide and 1-5 pts.wt. amine-based antioxidant. The contents of the filler comprising the carbon black and the titanium oxide are regulated so as to be 30-120 pts.wt. based on 100 pts.wt. rubber component. The tire is composed of the rubber composition. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition for a tire and a tire, and more particularly to a rubber composition for a tire capable of greatly improving weather resistance and discoloration resistance, and a tire comprising the rubber composition. .

[0002]

2. Description of the Related Art Conventional pneumatic tires are oxidatively deteriorated by oxygen and ozone in the air during long-term use, and cracks occur in the sidewalls and tread groove bottoms. The generation of cracks not only deteriorates the appearance of the tire, but also causes damage if the crack grows due to rolling of the tire, which causes deterioration of durability.

For this reason, various antiaging agents are generally added to rubber compositions for tires such as sidewalls, treads and chafers to prevent oxidative deterioration. The anti-aging agent has the role of precipitating on the surface upon receiving external stimuli such as temperature, strain and ozone, and preventing the deterioration reaction due to oxygen and ozone. Among the antiaging agents, amine antiaging agents have an excellent effect on weather resistance such as ozone resistance and therefore are used as essential for rubber compositions for tires.

However, if an attempt is made to obtain sufficient ozone resistance until the end of use of the tire by blending an antiaging agent, a relatively large amount of the antiaging agent (for example, 100 parts by weight of the rubber component is added in total). It is necessary to add 3 to 5 parts by weight or more of an antioxidant). Antiaging agents decompose over time due to light such as ultraviolet rays, and this decomposed product turns brown or brown and adheres firmly to the rubber surface.Thus, if a large amount of antiaging agent is used, the appearance of the tire will deteriorate. Therefore, there was a problem that the commercial value was reduced.

Conventionally, improvements have been investigated by adjusting the amount and blending of anti-aging agents, but it has been extremely difficult to achieve both weather resistance and discoloration resistance because of anti-trapping performance.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rubber composition for a tire, which can greatly improve weather resistance and discoloration resistance over a long period of time, and a tire comprising the rubber composition. And

[0007]

[Means for Solving the Problems] As a result of extensive studies to improve the above-mentioned various problems, titanium rubber having a high effect of concealing light such as ultraviolet rays, which greatly contributes to the decomposition of the antioxidant, has been found in a rubber composition for tires. It has been found that not only can the decomposition of the anti-aging agent be reduced and the discoloration resistance can be improved, but the synergistic effect of these can also improve the weather resistance over a long period of time.

That is, according to the present invention, 100 parts by weight of a rubber component, 10 to 100 parts by weight of carbon black having a nitrogen adsorption specific surface area of 20 to 150 m ² / g, and 5 to 5 parts of titanium oxide.
A tire rubber composition comprising 20 parts by weight and 1 to 5 parts by weight of an amine anti-aging agent, wherein the content of the filler containing the carbon black and the titanium oxide is 100 parts by weight of the rubber component. It relates to a rubber composition for a tire which is 30 to 120 parts by weight.

In the tire rubber composition, it is preferable that the titanium oxide has an average particle diameter of 1 μm or less.

The present invention further relates to a tire comprising the above rubber composition for tires.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition for tires of the present invention comprises
It consists of a rubber component, carbon black, titanium oxide and an amine anti-aging agent.

As the rubber component, natural rubber and / or
Alternatively, a diene-based synthetic rubber is used. Examples of the diene-based synthetic rubber include styrene-butadiene rubber (SB
R), butadiene rubber (BR), isoprene rubber (I
R), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) and the like. These may be contained in the rubber component in one kind or in two or more kinds.

The carbon adsorption specific surface area of the carbon black is 20 to 150 m ² / g. If the nitrogen adsorption specific surface area of carbon black is less than 20 m ² / g, the strength of the rubber composition for tires tends to be insufficient.
If it exceeds ² / g, the heat generation tends to increase.

Examples of the carbon black include GPF, FEF, HAF, ISAF, SAF, etc., but are not particularly limited.

The amount of the carbon black compounded is 10 to 100 parts by weight, preferably 30 to 70 parts by weight, based on 100 parts by weight of the rubber component. If the compounding amount of carbon black is less than 10 parts by weight, the strength of the rubber composition for tires tends to be insufficient, and if it is more than 100 parts by weight, heat generation is high and elongation at break tends to be significantly reduced. is there.

The average particle diameter of the titanium oxide is preferably 1 μm or less. The average particle size is measured by image analysis with an electron microscope. When the average particle diameter of titanium oxide is larger than 1 μm, the strength of the rubber composition for tires tends to be reduced.

The specific surface area of the titanium oxide measured by the BET method is preferably 15 to 50 m ² / g, more preferably 15 to 45 m ² / g. When the specific surface area of titanium oxide measured by the BET method is less than 15 m ² / g, the effects of sufficient ozone resistance and discoloration resistance tend not to be obtained, and when it exceeds 50 m ² / g, the cohesive force between titanium oxides is increased. It tends to be high and difficult to disperse.

The amount of titanium oxide compounded is 5 to 20 parts by weight, preferably 1 part by weight, based on 100 parts by weight of the rubber component.
It is 0 to 20 parts by weight. When the compounding amount of titanium oxide is less than 5 parts by weight, the effect of improving weather resistance and discoloration resistance is small.
Even if the amount is more than 0 parts by weight, the effect of further improving the weather resistance is not recognized, and on the contrary, the strength of the tire rubber composition tends to decrease.

Titanium oxide has heretofore been widely known as an inorganic pigment, and has been used as a white pigment for making rubber white. However, as in the present invention, for the purpose of improving weather resistance and discoloration resistance, there is no example in which a rubber composition containing carbon black used in a conventional tire is used in combination with titanium oxide and an amine anti-aging agent. It was

The rubber composition of the present invention may contain a filler other than the carbon black and titanium oxide. Examples of the filler other than carbon black and titanium oxide include inorganic powder such as silica represented by nM · xSiO _y · zH ₂ O. here,
M is a metal such as Al, Mg, Ti and Ca. n is 0
Is an integer from 5 to 5, x is an integer from 0 to 10, and y is 2
Is an integer of 5 and z is an integer of 0-10. Other examples include calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, alumina, clay, talc, magnesium oxide and the like. They are,
The rubber composition may contain one kind or two or more kinds.

The blending amount of the filler containing carbon black and titanium oxide is 30 to 120 parts by weight, preferably 35 to 100 parts by weight, based on 100 parts by weight of the rubber component. If the compounding amount of the filler is less than 30 parts by weight, the strength of the rubber composition for tires becomes insufficient, and if it is more than 120 parts by weight, the elongation at break tends to be significantly reduced.

Examples of the amine antiaging agent include amine derivatives such as diphenylamine and p-phenylenediamine. Examples of the diphenylamine-based derivative include p- (p-toluenesulfonylamide) -diphenylamine and octylated diphenylamine. As the p-phenylenediamine derivative, for example, N-phenyl-N ′-(1,
3-dimethylbutyl) -p-phenylenediamine, N-
Phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-2-naphthyl-p-phenylenediamine, N-1,3-dimethylbutyl-N'-phenyl-
Examples include p-phenylenediamine. In the present invention, the amine anti-aging agent is used because it has particularly excellent weather resistance among anti-aging agents.

The amount of the amine anti-aging agent is 1 to 5 parts by weight based on 100 parts by weight of the rubber component.
If the compounded amount of the amine anti-aging agent is less than 1 part by weight, the weather resistance is lowered, and if it exceeds 5 parts by weight, the discoloration resistance is lowered.

In the rubber composition of the present invention, in addition to the amine anti-aging agent, other anti-aging agents can be used in combination.

In the rubber composition for tires of the present invention, in addition to the above-mentioned components, for example, a softening agent such as wax, aroma-based, paraffin-based or naphthene-based process oil; stearic acid; zinc white; sulfur, peroxide. A compounding agent used in the usual rubber industry such as a vulcanizing agent such as a compound, a vulcanization accelerator, a silane coupling agent, etc., can be appropriately compounded as necessary within a range that does not impair the effects of the present invention. .

The tire rubber composition of the present invention contains the rubber component, carbon black, titanium oxide, an amine anti-aging agent and, if necessary, other compounding ingredients, in a conventional processing device such as a roll or a Banbury mixer. It can be obtained by kneading with a kneader.

The rubber composition for a tire of the present invention can be used, for example, in the sidewall portion, tread portion, chafer portion, etc. of a tire.

The tire of the present invention is produced by a usual method using the above rubber composition for a tire. That is,
The rubber composition for a tire is extruded into a shape of each member of the tire such as a sidewall portion, a tread portion, and a chafer portion at an unvulcanized stage, and is bonded by a usual method on a tire molding machine and unvulcanized. Mold a vulcanized tire. This unvulcanized tire is heated and pressed in a vulcanizer to obtain a tire.
The tire of the present invention thus obtained has significantly improved weather resistance and discoloration resistance over a long period of time.

[0029]

The present invention will be described in detail below based on examples, but the present invention is not limited to these.

Examples 1 to 3 and Comparative Examples 1 to 3 (Raw material) Natural rubber: RSS # 3 BR: BR150B HAF manufactured by Ube Industries Ltd. Carbon: Show Black N330 manufactured by Showa Cabot Corporation (adsorbed by nitrogen) Specific surface area: 72 m ² / g) Titanium oxide: A100 manufactured by Ishihara Sangyo Co., Ltd. (average particle size:
0.15 μm, BET specific surface area: 22 m ² / g) Amine anti-aging agent: Nocrac 6C (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. ) Wax: Sunnox wax aroma oil manufactured by Ouchi Shinko Chemical Co., Ltd .: JOMO process X140 manufactured by Japan Energy Co., Ltd. Stearic acid: Zinc stearate produced by NOF Corporation: Mitsui Mining & Smelting Co., Ltd. Zinc Hua No. 1 Sulfur Made by: Tsurumi Chemical Co., Ltd. Powder Sulfur Vulcanization Accelerator: Ouchi Shinko Chemical Co., Ltd. Nox Cellar N
S (N-tert-butyl-2-benzothiazylsulfenamide)

(Processing Method for Rubber Specimen) According to the formulation shown in Tables 1 and 2, the components other than sulfur and the vulcanization accelerator were kneaded with a BR type Banbury mixer to prepare a masterbatch. Then, the masterbatch, sulfur and vulcanization accelerator were kneaded with an 8-inch roll to obtain various test rubber compositions. These compounds were press-vulcanized at 170 ° C. for 15 minutes to obtain vulcanized products (rubber test pieces).

These were tested for the following characteristics.

(Evaluation of rubber test pieces) -Appearance of these test pieces was exposed outdoors so as not to be exposed to rain water, using a rubber plate having a thickness of 4 mm that was vulcanized in appearance. After exposure for 30 days, the appearance was visually observed and the degree of discoloration was evaluated on a scale of five. The smaller the value, the greater the degree of discoloration.

Test pieces left at 24 ° C. for 48 hours after vulcanization (constant temperature)
Then, the ozone resistance was measured for each of the test pieces (after the outdoor exposure) after the outdoor exposure for 30 days by the method described above. The measurement was performed according to JIS K6259. That is, after exposing the test piece for 96 hours continuously under the conditions of an ozone concentration of 50 ± 5 pphm and a tensile amount of 20 ± 2%, the test piece was taken out from the test tank and the crack state (the number of cracks and the size and depth of the cracks) was measured. , Was observed under the following conditions.

Number of cracks A: The number of cracks is small. B: Many cracks. C: There are numerous cracks.

Crack size and depth 1: There is a crack which is invisible to the naked eye but can be confirmed with a 10 × magnifying glass. 2: There is a crack that can be visually confirmed. 3: The crack is deep and relatively large (less than 1 mm). 4: Cracks are deep and large (1 mm or more and less than 3 mm). 5: There is a crack of 3 mm or more. Or is likely to cause a disconnection.

Flex fatigue resistance A flex crack initiation test was conducted in accordance with JIS K6260. The test conditions were such that after repeatedly bending 500,000 times, the state of cracks was evaluated by a series. The smaller the series, the better the bending fatigue resistance.

(Production Method of Tire) The rubber compositions obtained in Example 2 and Comparative Examples 1 and 2 were extruded into a sidewall member at the unvulcanized stage, and the tire was unvulcanized on a tire molding machine. Was molded. After that, by vulcanizing,
A tire having a tire size of 195 / 65R15 was obtained.

These were tested for the following characteristics.

(Evaluation with Tire) A durability test was carried out with a machine for a prototype tire. The test passes if there are no visible cracks and the vehicle completes 30,000 km. Further, the appearance of the tire after running for 30,000 km was confirmed based on the appearance discoloration evaluation method.

Table 2 shows the evaluation results of the rubber test pieces, and Table 3 shows the evaluation results of the tires.

In Comparative Example 1 in which titanium oxide was not mixed, the degree of discoloration in appearance was large in both the evaluation of the rubber test piece and the evaluation of the tire.

In Comparative Example 2 in which the compounding amount of titanium oxide exceeds 20 parts by weight, the flexural fatigue resistance was low in the evaluation of the rubber test piece, and cracks occurred in the durability test in the evaluation of the tire.

In Comparative Example 3 in which the amount of the amine anti-aging agent was less than 1 part by weight, the ozone resistance was low in the evaluation of the rubber test piece, and the number, size and depth of cracks were all large. It was

In Examples 1 to 3 in which an appropriate amount of titanium oxide and an amine antiaging agent were used, good results were obtained in the evaluation of rubber test pieces in terms of ozone resistance, discoloration of appearance, and flex fatigue resistance. Further, in Example 2, good results were obtained in the durability test and the appearance discoloration in tire evaluation.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

According to the present invention, by adding a specific amount of titanium oxide and an amine anti-aging agent to a conventional tire rubber composition, the weather resistance and discoloration resistance are greatly improved over a long period of time. be able to.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuyuki Nishioka             3-6-9 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo               Sumitomo Rubber Industries, Ltd. (72) Inventor Takuya Horiguchi             3-6-9 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo               Sumitomo Rubber Industries, Ltd. F-term (reference) 4J002 AC031 AC061 AC071 AC081                       AC091 BB151 DA036 DE137                       EN068 EN078 FD016 FD017                       FD068 GN01

Claims (3)

[Claims] 1. A carbon black 1 having 100 parts by weight of a rubber component and a nitrogen adsorption specific surface area of 20 to 150 m ² / g.
A rubber composition for a tire, comprising 0 to 100 parts by weight, 5 to 20 parts by weight of titanium oxide, and 1 to 5 parts by weight of an amine antioxidant, wherein the content of the filler containing the carbon black and the titanium oxide is A rubber composition for a tire, which is 30 to 120 parts by weight with respect to 100 parts by weight of the rubber component. 2. The rubber composition for a tire according to claim 1, wherein the titanium oxide has an average particle diameter of 1 μm or less. 3. A tire comprising the rubber composition for a tire according to claim 1.