JP3437784B2 - Rubber composition for sidewall - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a rubber composition for a side wall. More specifically, the present invention relates to a rubber composition for a sidewall having improved crack resistance and cut resistance by specifying the amounts of sulfur and a sulfenamide vulcanization accelerator. [0002] Conventionally, SFC resistance of rubber for sidewalls of pneumatic tires
In order to improve (Super Facial Cracking) properties, there is a technique of blending a low-grade carbon such as N660 or N550 to prevent stress concentration at an initial crack on a rubber surface. For example, JP-A-2-308833 discloses that, based on 100 parts by weight of a rubber component, 50 parts by weight of a low-carbon FEF, 1.5 parts by weight of sulfur, and 0.4 parts by weight of a sulfenamide-based vulcanization accelerator are used. It is described that the sidewall using the compounded rubber composition has good durability and appearance. However, low-grade carbon such as FEF has a low reinforcing property, and the rubber composition for a side wall containing the same has a problem that the cut resistance is low. Therefore, in applications such as heavy duty tires that are susceptible to cuts and damage due to collisions with stones on the road surface or road shoulders, it is usual to take measures by blending high-grade carbon such as N330 and N220. . For example, Japanese Patent Laid-Open No. 58-45
No. 240, JP-A-60-61315 and JP-A-8-325411 disclose that 45 to 50 parts by weight of a higher carbon such as HAF, 100 parts by weight of a rubber component, Disclosed is a rubber composition containing a sulfenamide vulcanization accelerator of 0.67 times to 2.1 times. [0004] However, in such a case, the hardness of the rubber tends to increase, and the SFC performance particularly at the beginning of running tends to decrease. After that, the SFC grows, leading to large cracks, and in some cases, the tires for heavy loads may not be able to be regenerated. For this reason, there is a problem that the crack resistance of the sidewall surface is reduced. SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a rubber composition for a side wall containing high-grade carbon, in which the amounts of sulfur and the sulfenamide-based vulcanization accelerator and the ratio thereof are specified. This is a result of a study for improving the crack resistance and the cut resistance without deteriorating the SFC resistance at the beginning of running by specifying. That is, according to the present invention, the amount of adsorbed iodine is 60 mg I ₂ / g or more (from 76 to 86 m
carbon black 40 to 60 parts by weight of gI except for the ₂ / g), 0 of sulfur 0.3 to 1.3 parts by weight of you and sulfur amount.
3 to 0.5 times a sulfenamide-based vulcanization accelerator for a sidewall rubber composition containing the composition 28
As a 5 / 75R 24.5 tire sidewall
After running 320,000 km, use the sidewall
Side walls with hardly any cuts on the rubber surface
The present invention relates to a rubber composition for rubber (Claim 1). DETAILED DESCRIPTION OF THE INVENTION As the rubber used in the rubber composition for a side wall of the present invention, a raw rubber generally used for a rubber composition for a side wall can be used without any particular limitation. . As the rubber, for example, natural rubber (N
R), butadiene rubber (BR), isoprene rubber (I
R), styrene-butadiene rubber (SBR), butyl rubber (IIR), brominated p-methylstyrene-isobutylene copolymer, and the like. These may be used alone or in combination of two or more. In particular, a blend of high cis-butadiene rubber having an effect of suppressing crack growth and natural rubber having high breaking strength and excellent cut resistance is preferable. The carbon black used in the rubber composition for a side wall of the present invention has an iodine adsorption amount of at least 60 mgI ₂ / g measured according to JIS K6221.
(Showa Cabot Co., Ltd. Show Black N330
A c except 76~86mgI ₂ / g is iodine adsorption). If the amount of iodine adsorbed is less than 60 mgI ₂ / g, the reinforcing properties are not sufficient, and the cut resistance of the rubber composition for sidewalls decreases. The compounding amount of the carbon black is 40 to 60 parts by weight based on 100 parts by weight of the rubber component.
If the amount is less than 40 parts by weight, sufficient strength cannot be obtained and cut resistance becomes insufficient. If the amount exceeds 60 parts by weight, hardness increases and crack growth resistance becomes insufficient. The carbon black can be used without any particular limitation as long as it has the above characteristics. For example, SAF (about 136 mg I ₂ / g), ISAF (about 119 mg I ₂ / g), IISAF-HS (about 106 m I / g)
gI ₂ / g), HAF (about 80 mg I ₂ / g), LM-H
AF and the like. These may be used alone,
Two or more kinds may be used in combination. [0012] The rubber composition for a side wall of the present invention, relative to the rubber component 100 parts by weight, sulfur 0. 3 ~
1.3 parts by weight and 0.3 to 0.5 times the sulfur compounding amount of the sulfenamide-based vulcanization accelerator are compounded. In addition,
As long as the sulfenamide-based vulcanization accelerator is within the above-mentioned range, other vulcanization accelerators (such as thiazole-based vulcanization accelerators) may be used in an amount of less than 20% by weight of the total vulcanization accelerator. You may use together. 1.3 parts by weight of the sulfur
Exceeding the running initial resistance SFC performance, resistance to cracking performance is lowered, when less than 0.3 part by weight, sufficient vulcanization performance can not be obtained, it occurs a tendency such under-cured (insufficient vulcanization) . When the amount of the sulfenamide-based vulcanization accelerator is less than 0.3 times the amount of sulfur, undercuring still occurs, and when it exceeds 0.5 times, the SFC resistance and crack resistance in the initial stage of running are also increased. Decreases. The sulfenamide-based vulcanization accelerator is not particularly limited, but N-substituted-2-benzothiazol-sulfenamide is preferred.
tert-butyl-2-benzothiazol-sulfenamide (BBS), N-oxydiethylene-2-benzothiazol-sulfenamide (OBS), N, N-diisopropyl-2-benzothiazol-sulfenamide (DP
BS), N-cyclohexyl-2-benzothiazol-sulfenamide (CBS) and the like. In addition to the above, various additives commonly used in the rubber industry, such as a softening agent for rubber, an antioxidant, stearic acid, and zinc oxide, are added to the rubber composition for a sidewall of the present invention. be able to. The rubber composition for a side wall of the present invention comprises:
Except for using the raw materials in the above-mentioned amounts, the raw materials can be obtained by a known method and under conditions common to those skilled in the art. It is suitably provided. EXAMPLES Next, the rubber composition for a side wall of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The raw materials and evaluation methods used in the examples and comparative examples are described below. Natural rubber: ordinary RSS # 3 butadiene rubber: BR150B (trade name) manufactured by Ube Industries, Ltd. N220: Show Black N manufactured by Showa Cabot Co., Ltd.
220 (trade name), iodine adsorption amount 119 mg I ₂ / g N330: Show Black N manufactured by Showa Cabot Co., Ltd.
330 (trade name), iodine adsorption amount 67 mg I ₂ / g N660: diamond black G (trade name) manufactured by Mitsubishi Chemical Corporation, iodine adsorption amount 24 mg I ₂ / g sulfur: powder sulfur vulcanization manufactured by Karuizawa Sulfur Co., Ltd. Accelerator: Noxeller N manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
S (trade name) (N-tert-butyl-2-benzothiazole sulfenamide) Process oil: Diana Process AH-24 (trade name) manufactured by Idemitsu Kosan Co., Ltd. Anti-aging agent: manufactured by Sumitomo Chemical Co., Ltd. Antigen 6C (trade name) (N-1,3-dimethylbutyl-N'-phenyl-
(P-phenylenediamine) Stearic acid: Nippon Yushi Co., Ltd. stearic acid “Tsubaki” (trade name) Zinc flower: Two types of zinc oxide manufactured by Mitsui Kinzoku Mining Co., Ltd. [Evaluation by actual vehicle test] Predetermined tire A 320,000 km actual vehicle test was conducted on the market by using, and evaluated according to the following criteria. When the rubber surface of the side wall is distorted by a driver at the time of running 30,000 km, cracks of 0.5 mm or more are already recognized: × 30,000 km after running at 30,000 km Cracks of less than 0.5 mm are observed when the rubber surface of the wall is distorted by a driver: ○ Almost all cracks are observed when the rubber surface of the sidewall is distorted by a driver after traveling 30,000 km. Not possible: ◎ Cracking resistance at the end of running After running 320,000 km, many cracks of about 5 mm in appearance are recognized on the rubber surface of the sidewall:
× Cracks of about 2 to 5 mm are apparently observed on the rubber surface of the sidewall after running 320,000 km: ○ Cut resistance during running After running 320,000 km, a large cut was found on the rubber surface of the sidewall. A lot of things are recognized: × A small cut is slightly observed on the rubber surface of the sidewall after traveling 320,000 km: ○ A little cut is found on the rubber surface of the sidewall after traveling 320,000 km: ◎ [0021] example 1 Contact and Comparative examples a, b, raw materials 1-3 Table 1 describes (except sulfur and the vulcanization accelerator) were blended so that the composition shown in Table 1, using a Banbury mixer Kneaded. The obtained kneaded product was blended with sulfur and a vulcanization accelerator in the amounts shown in Table 1, and further kneaded with a Banbury mixer to obtain a green rubber composition. Next, a tire of 285 / 75R24.5 in which each green rubber composition was provided on a side wall was prepared and subjected to evaluation. Table 1 shows the results. [Table 1] From the results in Table 1, it can be seen that the tires using the rubber compositions of the respective examples in which sulfur and the vulcanization accelerator were blended within the scope of the present invention, despite the fact that all used high-grade carbon black, It can be seen that it has excellent SFC resistance at the beginning of traveling, crack resistance at the end of traveling, and cut resistance during traveling. On the other hand, Comparative Example 1 using lower carbon black, Comparative Example 2 in which the amount of sulfur exceeds the range of the present invention,
The tire using the rubber composition of Comparative Example 3 in which the use ratio of sulfur and the vulcanization accelerator was out of the range of the present invention was obtained.
It can be seen that any of the FC performance, the crack resistance at the end of running, and the cut resistance during running is inferior to those of the examples. According to the present invention, a rubber composition for sidewalls having improved crack resistance and cut resistance by specifying the amounts of sulfur and sulfenamide-based vulcanization accelerators. Can be obtained.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L ⁷ /00-21/00 B60C 1/00 C08K 3/04 C08K 3/06 C08K 5/44

Claims (1)

(57) [Claims 1] The iodine adsorption amount is 60 mg I ₂ / g or more ( excluding 76 to 86 mg I ₂ / g ) per 100 parts by weight of rubber.
40 to 60 parts by weight of carbon black, sulfur 0.3 to
1.3 parts by weight and Contact and sulfur amount sidewall rubber composition containing 0.3 to 0.5 times the sulfenamide vulcanization accelerator, the composition 285 / 75R 2
Used as a sidewall for 4.5 tires, 320,000
After traveling kilometers, the rubber surface
Rubber composition for sidewalls with almost no cut
Thing .