JPH09136996A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire excellent in braking performance, control stability and wear resistance not only on wetted roadways but also on conventional pavements. SOLUTION: In a radial tire provided with a tread section having a plurality of blocks or ribs formed by dividing the tread surface by at least two circumferential main grooves of the tire, the tread section comprises a rubber composition comprising 100 pts.wt. of a rubber component containing at least 40 pts.wt. SBR having a styrene content of 20-60%, 20 pts.wt. or more of silica having an SA (specific surface for nitrogen adsorption) of 130-280m<2> /g of N2 , 70-120 pts.wt. in total of carbon black having an SA of 80-280m<2> /g of N2 and the silica, and 5-40 pts.wt. rosin from natural resin, the rubber composition having a 25 deg.C JIS hardness in excess of 65 deg..

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 particularly to a high performance pneumatic radial tire excellent in braking performance, steering stability and wear resistance not only on wet road surfaces but also on general paved road surfaces. Regarding

[0002]

2. Description of the Related Art With the recent increase in speed of automobiles, the characteristics required for tires have become stricter, and pneumatic radial tires with higher limit performance in terms of braking performance, steering stability, high-speed durability, etc. Was strongly requested.

In order to solve this, various studies have been made, and many techniques focusing on the rubber composition surface of the tread are known. To improve the braking performance, increase the grip force with the road surface, that is, the frictional force, and to improve the steering stability, increase the block rigidity of the tread pattern,
In order to improve the cornering property and improve the durability, it is possible to improve the breaking property.

Japanese Unexamined Patent Publication (Kokai) No. 58-1734 describes a rubber composition having a large hysteresis loss and intends to improve the frictional force. In order to obtain a rubber composition having a large hysteresis loss, generally, a softening agent such as aromatic oil or a reinforcing agent such as carbon black is increased, or vulcanization is adjusted to lower the vulcanization density. There is. On the other hand, by adding silica to the rubber composition, -20 to 20 ° C
The hysteresis loss in the small strain range in the temperature range is increased, and the elastic modulus is set so that the contact area can be secured by following the unevenness of the road surface, and various performances such as braking performance and steering stability on wet road surface can be obtained. It has improved.

[0005]

However, in the method of using a rubber composition in which the hysteresis loss is increased by increasing the amount of the softening agent or the reinforcing agent to an appropriate amount or more, the breaking strength and the block rigidity are lowered, and the tire suddenly increases. It becomes difficult to continue cornering and high speed driving.

Further, although the tire using the silica-containing rubber composition has improved wet performance on wet road surfaces, the friction performance on general pavement road surfaces is reduced, that is, the braking performance is deteriorated due to a reduction in grip force, and wear skin is further reduced. Is seen, and both braking performance and steering stability on both road surfaces cannot be achieved at the same time.

Therefore, an object of the present invention is to provide a pneumatic radial tire excellent in braking performance, steering stability and wear resistance not only on wet road surfaces but also on general paved road surfaces.

[0008]

In order to solve the above-mentioned problems, the present inventor has paid close attention to rubber species, characteristics of fillers, other compounding agents, etc. The inventors have found that the characteristics can be satisfied at the same time, and have completed the present invention. (1) The pneumatic radial tire of the present invention is a pneumatic radial tire including a tread portion having a plurality of blocks or ribs, which divides the tread surface by at least two circumferential main grooves extending in the tire circumferential direction. At
The tread portion is 130 to 280 m ² / g based on 100 parts by weight of a rubber component containing at least 40 parts by weight of styrene-butadiene rubber having a styrene content of 20 to 60%.
20 parts by weight or more of silica having a nitrogen adsorption specific surface area of 80 to 280 m ² / g and a total amount of carbon black having a nitrogen adsorption specific surface area of 80 to 280 m ² / g of 70 to
A rubber composition containing 120 parts by weight and 5 to 40 parts by weight of a natural resin-based rosin, and the rubber composition contains 65 parts by weight.
It is characterized by having a JIS hardness of 25 ° C. exceeding 0 °. (2) The pneumatic radial tire of the present invention is characterized in that, in the item (1), the rubber composition contains 30 to 70 parts by weight of silica. (3) The pneumatic radial tire of the present invention is characterized in that, in the above item (1), the rubber composition contains 80 to 110 parts by weight of carbon black in a total amount with silica. (4) The pneumatic radial tire of the present invention is characterized in that in the above (1), the rubber composition contains 20 parts by weight or more of carbon black. (5) In the pneumatic radial tire of the present invention, in the item (1), the rubber composition contains 10 to 10 natural resin rosin.
35 parts by weight is included. (6) The pneumatic radial tire of the present invention is characterized in that, in the above item (1), the rubber composition contains a silane coupling agent in an amount of 3 to 20% by weight of silica.

The rubber component used in the present invention is 20 to 6
Styrene-butadiene rubber (SBR) having a styrene content of 0%, preferably 30 to 45% from the viewpoint of effect,
At least 40 parts by weight is included with respect to 100 parts by weight of the rubber component. The SBR is not particularly limited as long as it satisfies the styrene content, but includes emulsion polymerization SBR, solution polymerization SBR and the like. The composition distribution of the styrene unit and the butadiene unit of the SBR may be any of random type, block type and intermediate type thereof, but the random type or intermediate type is preferable. SB
The vinyl content of the butadiene portion of R is 10 to 10 of the butadiene portion.
It is about 80%.

When the styrene content of SBR is less than 20%, it is inconvenient because the desired gripping force in the low temperature to high temperature range cannot be obtained, and when it exceeds 60%, the rubber-likeness decreases and the road surface of the rubber decreases. Since it is less likely to bite into it, a desired grip force cannot be obtained, which is not preferable. If the blending amount of SBR is less than 40 parts by weight, the desired grip force in the low temperature range cannot be obtained.

The rubber component used in the present invention can be obtained by mixing 60 parts by weight or less of natural rubber or synthetic rubber with the above SBR. Examples of this synthetic rubber include SBR other than the SBR specified in the present invention, high cis-1,4-
Examples thereof include polybutadiene, medium cis-1,4-polybutadiene, high cis-1,4-polyisoprene and halogenated butyl rubber.

The rubber composition of the present invention contains 130 to 2
Silica having a nitrogen adsorption specific surface area (N ₂ SA) of 80 m ² / g is included in an amount of 20 parts by weight or more, but preferably 30 to 70 parts by weight from the viewpoint of the effect. Silica includes anhydrous silicic acid (dry silica) and hydrous silicic acid (wet silica),
Wet silica is preferred. When N ₂ SA is less than 130 m ² / g, sufficient elastic modulus cannot be obtained and wear resistance is deteriorated.
When it exceeds 0 m ² / g, it is not preferable because the kneading workability is deteriorated although the improvement of the grip force cannot be expected so much. If the amount of silica is less than 20 parts by weight, the grip force on a wet road surface will be insufficient.

The rubber composition of the present invention contains 80 to 28
Carbon black having 0 m ² / g of N ₂ SA is contained in an amount of 70 to 120 parts by weight in total with silica.
From the viewpoint of effect, it is preferably contained in an amount of 80 to 110 parts by weight. N
_{When 2} SA is less than 80 m ² / g, sufficient elastic modulus cannot be obtained and wear resistance becomes poor. When it exceeds 280 m ² / g, improvement in grip strength and wear resistance cannot be expected, but
This is not preferable because the kneading workability is reduced. If the total amount of carbon black and silica is less than 70 parts by weight, sufficient gripping force cannot be obtained, and if it exceeds 120 parts by weight, sufficient abrasion resistance cannot be obtained. Further, it is preferable that 20 parts by weight or more of carbon black is blended in the rubber composition from the viewpoint of the effect.

The rubber composition of the present invention contains 5 to 40 parts by weight of a natural resin rosin, and preferably 10 to 35 parts by weight from the viewpoint of achieving both grip strength and abrasion resistance. Examples of the natural resin rosin include rosin and rosin derivatives (eg hydrogenated rosin, rosin esters, etc.). When the amount of the natural resin-based rosin is less than 5 parts by weight, the effect of addition such as improvement in grip strength is small, and when it exceeds 40 parts by weight, abrasion resistance is deteriorated, which is not preferable.

The rubber composition according to the present invention has a JIS hardness of 25 ° C. exceeding 65 °. If the JIS hardness at 25 ° C. is 65 ° or less, the grip force and abrasion resistance become insufficient, which is not preferable.

The rubber composition may contain a silane coupling agent in an amount of 3 to 20% by weight of silica.
The silane coupling agent has the action of strengthening the bond between silica and the rubber component, and can improve the modulus in large deformation. If the amount of the silane coupling agent is less than 3% by weight, the effect of adding the silane coupling agent does not appear, and if it exceeds 20% by weight, the cost is increased but the effect is not obtained.

Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2 -Trimethoxysilylethyl)
Tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane , 3-chloropropyltrimethoxysilane, 3
-Chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, N -Dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxy Silylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-me Captopropyldimethoxymethylsilane, 3-nitropropyldimethoxymethylsilane, 3-chloropropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, dimethoxymethylsilylpropylbenzothiazoletetrasulfide and the like, Bis (3-triethoxysilylpropyl) tetrasulfide, 3-trimethoxysilylpropyl benzothiazole tetrasulfide and the like are preferable.

The rubber composition used in the pneumatic radial tire of the present invention includes the compounding agents usually used in the rubber industry, such as other reinforcing fillers, vulcanizing agents, stearic acid,
Zinc oxide, a vulcanization accelerator, an antiaging agent, a softening agent and the like can be appropriately added.

[0019]

EXAMPLES A pneumatic radial tire of the present invention is provided with a tread portion having a plurality of blocks or ribs, which divides the tread tread surface by at least two circumferential main grooves extending in the tire circumferential direction, and one of the tread portions is provided. Part or all, preferably the whole, is composed of the rubber composition. Example 1
The tires used in Comparative Examples 1 to 3 are 225 / 50R16 size radial tires having the tread pattern shown in the pattern when the tire touches the ground in FIG.

The measuring methods for various laboratory tests and tire tests are as follows. -Measurement of styrene content It was determined by the absorption intensity of aromatic protons in a nuclear magnetic resonance (NMR) spectrum. -Measurement of nitrogen adsorption specific surface area (N ₂ SA) Based on ASTM D3037, the specific surface area (m ² ) per 1 g of carbon black was determined from the adsorption amount of nitrogen. -Measurement of JIS hardness According to JIS K6301, the hardness was measured at 25 ° C with a spring type hardness tester A type. -Measurement of lab WET-μ WET-μ is measured as an index of the braking performance of a tire on a wet road surface. The frictional force on a wet road surface was measured at 20 ° C. using a road surface friction tester (disclosed in Japanese Utility Model Publication No. 5-66545), and the value of Comparative Example 1 was 10
An index of 0 was displayed. The larger the value, the better the braking performance. -Measurement of Lab Abrasion Resistance Using a Lambourn abrasion tester, the slip ratio was measured at 25%, and the value of Comparative Example 1 was set as 100 and displayed as an index.
Larger numbers are better. -Measurement of tire Cp and CFmax This is measured as an index of the steering stability of the tire on a general pavement surface. Cp represents responsiveness when the steering wheel is turned, and CFmax represents grip.
Both of them use a flat belt manufactured by MTS and have a speed of 5
The measurement was performed under the conditions of 0 km / hour and a load of 400 kg. In addition,
Cp was the cornering force when the slip angle was 1 ° C. In each case, the value of Comparative Example 1 was set to 100 and displayed as an index. The larger the value, the better.

Example 1 SBR, carbon black,
Using silica, a silane coupling agent, rosin, etc., a rubber composition was prepared according to the compounding disposal in Table 1, and 145
Vulcanization was performed at 33 ° C. for 33 minutes. The JIS hardness, Labo WET-μ index and Labo abrasion index of the vulcanized product were measured. Table 2 shows the results. Cp and CFmax were measured for a pneumatic radial tire using this rubber composition as a tread. Table 2 shows the results.

Comparative Example 1 An experiment was conducted in the same manner as in Example 1 except that silica, silane coupling agent, rosin and the like were not used. The results of measuring various physical properties are shown in Table 2.

[Comparative Examples 2 to 3] The same experiment as in Example 1 was carried out except that rosin was not used. The results of measuring various characteristics are shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

As shown in Table 2, the pneumatic radial tire of the present invention has a braking performance especially on a wet road surface.
It can be seen that the steering stability and wear resistance on dry road surfaces are all at a high level and are well-balanced and improved.

As can be seen from the comparative examples, a tire (comparative example 1) using a rubber composition containing no silica or rosin and having a JIS hardness outside the scope of the claims (Comparative Example 1) has braking performance, steering stability and wear resistance. Neither is good. Further, the tires using the rubber composition not containing rosin and having the JIS hardness out of the range (Comparative Examples 2 to 3) have good wet braking performance, but have poor dry steering stability and wear resistance, resulting in poor wet surface resistance. It can be seen that the effect and the effect of dry road surface are not compatible.

[0028]

Since the pneumatic radial tire of the present invention has the above-mentioned constitution, it exerts an excellent effect that braking performance, steering stability and wear resistance are improved not only on a lubricated road surface but also on a general paved road surface. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a tread pattern when a pneumatic radial tire according to an embodiment of the present invention is in contact with a ground.

Claims (6)

[Claims] 1. A pneumatic radial tire provided with a tread portion having a plurality of blocks or ribs, which divides the tread surface by at least two circumferential main grooves extending in the tire circumferential direction, the tread portion comprising: 20 parts by weight or more of silica having a nitrogen adsorption specific surface area of 130 to 280 m ² / g, and 100 parts by weight of a rubber component containing at least 40 parts by weight of styrene-butadiene rubber having a styrene content of 20 to 60%; Carbon black having a nitrogen adsorption specific surface area of 280 m ² / g in a total amount of 70 to 12 with silica.
A rubber composition containing 0 part by weight and 5 to 40 parts by weight of a natural resin rosin, wherein the rubber composition has a temperature of more than 65 ° C.
A pneumatic radial tire having an IS hardness. 2. The pneumatic radial tire according to claim 1, wherein the rubber composition contains 30 to 70 parts by weight of silica. 3. The rubber composition comprises carbon black,
The pneumatic radial tire according to claim 1, wherein the total amount of silica and the silica is 80 to 110 parts by weight. 4. The rubber composition comprises carbon black 2
The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire contains 0 part by weight or more. 5. The natural rubber-based rosin is used as the rubber composition.
The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire contains 0 to 35 parts by weight. 6. The pneumatic radial tire according to claim 1, wherein the rubber composition contains a silane coupling agent in an amount of 3 to 20% by weight of silica.