JPH08175120A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE: To achieve the excellent balance of the bending and fatigue resistance, the rolling resistance and the cutting resistance of a pneumatic tire. CONSTITUTION: A black side wall part of a tire is composed of the rubber component containing 100 pts.wt. rubber having the composition consisting of, by weight, <=25% styrene, 5-20% styrene-butadiene copolymer rubber of high vinyl content where 1,2-vinyl bond is >=60%, and 95-80% diene rubber containing >35% natural rubber, and 35-60 pts.wt. carbon black.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more specifically, to a flex side of a tire by blending a specific high vinyl styrene-butadiene copolymer rubber (high vinyl SBR) in the black sidewall portion of the tire. Fatigue,
The present invention relates to a pneumatic radial tire having excellent rolling resistance and cut resistance.

[0002]

2. Description of the Related Art In recent years, measures against automobile exhaust gas have become necessary from the viewpoint of environmental protection, and the emission amount of carbon dioxide contained in the exhaust gas has become a problem.
From this point of view, it is required to reduce the exhaust gas amount and the fuel consumption of automobiles, and it is necessary to reduce the weight of tires and achieve low rolling resistance. If the black sidewall portion is thinned in order to reduce the weight of the tire for such a purpose, the cut resistance of the tire becomes inferior, which is not preferable. Therefore, it is necessary to improve the cut resistance.

Attempts have been made to improve flex fatigue resistance and cut resistance by using a high cis polybutadiene / natural rubber compound in the sidewall portion of a tire, for example, JP-A-57-341.
No. 41, No. 60-61315, No. 6
However, the effect is not always sufficient. Further, in place of high cis polybutadiene, an attempt to achieve both rolling resistance and flex fatigue resistance by using high vinyl or medium vinyl polybutadiene or styrene-butadiene copolymer rubber has been disclosed, for example, in Japanese Unexamined Patent Publication (KOKAI) No. Sho 5-
Although proposed in JP-A-7-25339 and JP-A-61-188201, these have not yet satisfied all the desired flex fatigue resistance, cut resistance and rolling resistance of the tire.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention eliminates the above-mentioned problems of the prior art, and provides an air which is excellent in all of tire fatigue resistance, rolling resistance and cut resistance. It is intended to provide a filled radial tire.

[0005]

According to the present invention, (i)
A diene containing (a) 5 to 20% by weight of a high vinyl content styrene-butadiene copolymer rubber having a styrene content of 25% or less and a 1,2-vinyl bond content of 60% or more, and (b) a natural rubber of more than 35% by weight. 100 parts by weight of rubber containing 95 to 80% by weight of system rubber and (ii) carbon black 35 to 60
Provided is a pneumatic radial tire having a black sidewall portion of a tire formed from a rubber composition containing parts by weight.

[0006]

The function and effect of the present invention will be described in detail below. The structure of the pneumatic radial tire according to the present invention is not particularly limited, and not only a pneumatic radial tire of any conventionally known structure, but also a pneumatic radial tire of various structures currently under development. The structure can be As described above, the present invention includes any pneumatic radial tire in which the black sidewall portion of the tire is composed of the rubber composition having the above-mentioned constitution.

The rubber composition constituting the black sidewall portion of the pneumatic radial tire according to the present invention is
(I) (a) High vinyl content styrene having a styrene content of 25% by weight or less, preferably 14 to 22% by weight, and a 1,2-vinyl bond of 60% or more, preferably 61 to 77%.
5 to 20 parts by weight of butadiene copolymer rubber (high vinyl SBR), 95 to 80 parts by weight of diene rubber containing (b) more than 35 parts by weight of natural rubber (NR) (total amount of (a) and (b) 100) Parts by weight). The vinyl content here is the butadiene portion of SBR (cis, trans and vinyl).
The vinyl content in the product. The cis content in SBR is not particularly limited, but is preferably 5 to 15% by weight. The diene rubber can be any rubber that has been generally blended with a rubber composition that constitutes the black sidewall portion of a tire. As such rubber,
For example, natural rubber (NR), polybutadiene rubber (B
R), various styrene-butadiene copolymer rubbers (SB
R), polyisoprene rubber (IR) and the like, which can be used alone or as a blend in any ratio. Among these, as the diene rubber used in the present invention, the NR must be more than 35% by weight, and the preferable NR is 40 to 50% by weight and BR is 60 to 50% by weight.
It is preferable to use a blended rubber of 50% by weight in order to obtain desired physical properties.

If the blending amount of the high vinyl SBR used in the present invention is too small, the cut resistance is not sufficiently improved, and conversely, if the blending amount of the high vinyl SBR is too large, the crack resistance is increased. According to the knowledge of the present inventors, although the present invention is not intended to be limited to this, styrene in SBR contributes to improvement of cut resistance, but decreases bending fatigue resistance, whereas styrene in SBR decreases The vinyl bond contributes to a reduction in hysteresis (rolling resistance). Therefore, it is preferable to add a relatively large amount of vinyl to the black sidewall portion and maintain an appropriate amount of styrene.

The rubber composition constituting the black sidewall portion of the pneumatic radial tire of the present invention further contains carbon black as an essential component.

The carbon black used in the rubber composition according to the present invention is a carbon black generally used in rubber compounds, preferably a nitrogen specific surface area (N ₂ S
A) 20 to 130 m ² / g, more preferably 38 to 92 m ²
/ G, DBP (dibutyl phthalate) oil absorption 70ml / 1
00g or more, more preferably 99-130ml / 100g
Can be mentioned. According to the invention, such carbon black is used in an amount of 35-60 phr, preferably 40-55 ph.
r compound.

In the rubber composition for tires of the present invention, in addition to the above essential components, various kinds of sulfur, vulcanization accelerators, antioxidants, fillers, softeners, plasticizers and the like which are generally blended for tires are used. Additives can be blended and such blends can be vulcanized by conventional methods to produce tire treads. The compounding amount of these additives may be a general amount. For example, the compounding amount of sulfur is preferably 0.8 parts by weight or more per 100 parts by weight of rubber, and 1.0 to
More preferably, it is 2.0 parts by weight.

[0012]

The present invention will be described in more detail below with reference to Examples and Comparative Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples. Examples 1 to 6 and Comparative Examples 1 to 8 Each component was blended in the formulation (parts by weight) shown in Table I,
After mixing the vulcanization accelerator and the raw material rubber and compounding agent excluding sulfur for 5 minutes with a 16-liter Banbury mixer, kneading the mixture with the vulcanization accelerator and sulfur for 4 minutes in the same Banbury mixer to obtain a rubber composition. I got a thing. A test vehicle (domestic FF sedan vehicle) fitted with a pneumatic radial tire (size: 195 / 55R16) having a general structure for rolling resistance, flex crack resistance and cut resistance of the compound thus obtained It was measured by the above and shown in Table I.

(1) The composition used in the formulation of the examples and comparative examples
Mixture polymer A: High vinyl SBR (NS manufactured by Zeon Corporation NS
110, styrene content = 14%, 1,2-vinyl content =
77%) Polymer B: High vinyl SBR (NS manufactured by Zeon Corporation)
116, styrene content = 20%, 1,2-vinyl content =
67%) Polymer C: High vinyl SBR (test sample,
Styrene content = 21%, 1,2-vinyl content = 61%) Polymer D ^* : High vinyl SBR (test sample,
Styrene content = 22%, 1,2-vinyl content = 55%) Polymer E ^* : High vinyl SBR (SN manufactured by Zeon Corporation SN)
178, styrene content = 28%, 1,2-vinyl content =
64%) * Comparative sample

NR: RSS # 3 BR: NIPOL BR1220 manufactured by Zeon Corporation

Carbon black: N ₂ SA = 76 m ²
/ G, DBP = 100ml / 100g (Note) Method for measuring characteristics of carbon black (a) Nitrogen specific surface area (N ₂ SA) ASTM-D3037-78 "Standard Methods of Treating Carbon
Black-Surface Area by Nitrogen Adsorption "Method
By C. (B) Dibutyl phthalate oil absorption (DBP oil absorption) According to JIS K6221 "Rubber carbon black test method" 6.1.2 (1) A method. (C) 24M4DBP oil absorption amount According to ASTM-D3493. (D) ΔDBP DBP oil absorption −24M4 DBP oil absorption.

Aromatic oil: "Process oil X-140" manufactured by Kyodo Oil Co., Ltd. Zinc flower: "Zinc flower 3" manufactured by Shodo Kagaku Co., Ltd.
No. ”Stearic acid:“ Lunac ”manufactured by Kao Soap Co., Ltd.
ya "anti-aging agent: N-phenyl-N '-(1,3
-Dimethyl) -p-phenylenediamine (Sumitomo Chemical Co., Ltd. "Antigen 6C") Wax: Ouchi Shinko Chemical Co., Ltd. "Sunnock" Sulfur: Oil treatment sulfur Vulcanization accelerator: N-tert-butyl- 2-benzotizoyl-sulfenamide (Ouchi Shinko Chemical Co., Ltd.)
"Nox Cellar NS-F")

(2) Tire performance evaluation test method (tire support
165 SR13) 1) Rolling resistance Air pressure is 1.9 kg / on an indoor drum with a diameter of 1707 mm.
The rolling resistance of 80 km / hr was measured under the conditions of cm ² and load of 420 kg, and the rolling resistance of the tire of Experiment 1 was expressed as an index when the rolling resistance was 100. The smaller the index, the lower the rolling resistance. 2) Bending crack resistance A female cut 4 is formed at the center of the sidewall every 90 ° in the circumferential direction and forms an angle of 45 ° with the radial direction of 5 mm in length.
5000 pieces at a speed of 81km / hr on an indoor durability test drum under the conditions of air pressure 1.8kg / cm ² and load 361kg.
The length of the crack after traveling for km was measured and expressed as an index. The smaller the index, the greater the flex crack resistance (the better). 3) Cut resistance With the tip shape shown in Fig. 1, the weight of the entire load is 15 kg.
An impact force was applied to the center of the side of the tire inflated at a pressure of 1.8 kg / cm ² by dropping it from a height of m, and the number of times until destruction was measured.
It was shown by the index when. The larger the index, the better the cut resistance. The weight was dropped such that the length direction of the weight tip coincides with the direction of the carcass cord.

[0018]

[Table 1]

[0019]

EFFECTS OF THE INVENTION In Table I, Comparative Example 1 is a standard formulation example of the black sidewall portion, and other examples and comparative examples were evaluated based on this. Examples 1 to 6 show examples of the present invention, and as is clear from the results of Table I, according to the present invention,
The cut resistance can be improved while substantially maintaining the rolling resistance and the flex crack resistance (see Examples 1 to 6). As shown in the results of Comparative Examples 1 to 4 and Examples 1 to 3, the cut resistance is improved as the blending amount of the polymer B is increased, but the flex crack resistance is deteriorated when the blending amount exceeds 20 phr. . As is clear from Comparative Examples 1 and 5 to 6, when the natural rubber (NR) content is small (35 phr).
(In the following), the balance of physical properties becomes poor, which is not preferable. Further, as is clear from Comparative Examples 6 and 7, when the vinyl content of the high vinyl content SBR is less than 60%, rolling resistance is poor, and when the styrene content exceeds 25%, flex fatigue resistance is poor. As described above, according to the present invention, it is possible to obtain a pneumatic radial tire having excellent flex fatigue resistance, rolling resistance, and cut resistance.

[Brief description of drawings]

FIG. 1 is a drawing of a weight used in a cut resistance test.

Claims (1)

[Claims] 1. A high vinyl content styrene-butadiene copolymer rubber having a styrene content of (a) 25% or less and a 1,2-vinyl bond content of 60% or more (5 to 20% by weight), and (b) natural. 95% diene rubber containing more than 35% by weight of rubber
A pneumatic radial tire characterized in that the black sidewall portion of the tire is constituted by a rubber composition containing 100 parts by weight of a rubber component containing 80% by weight and (ii) 35 to 60 parts by weight of carbon black.