JPH0959433A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire markedly improved in performances in dry and wet states and being excellent in abrasion resistance and rolling resistance. SOLUTION: This pneumatic tire has a cap tread made of a rubber composition prepared by mixing 10 pts.wt. diene rubber containing 80 pts.wt. or above emulsion-polymerized styrene/polybutadiene rubber having a styrene content of 20-50wt.%, a cis content in the butadiene part of 15% or below and a weight- average molecular weight of 500,000 or above with 30-70 pts.wt. carbon black having a nitrogen absorption specific surface area (N2 SA) of 140m<2> /g or above, a 24M4DBP absorption of 90ml/100g or above, and the half-width (ΔDst) of an aggregate distribution as measured by the centrifugal settling method of 50μm or below, and 10-40 pts.wt. silica, and having a total content of the carbon black and the silica of 70-100 pts.wt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more specifically, by using a specific polymer and a carbon black / silica compound type rubber composition as a cap tread rubber, the dry and wet performances of the tire are significantly improved. The present invention relates to a pneumatic tire that is improved and has excellent wear resistance and rolling resistance.

[0002]

The tread portion of a pneumatic tire is generally composed of an outer layer side cap tread and an inner layer side undertread portion. Such pneumatic tires are required to have various performances, but it is particularly desired to achieve high-order balance between wet and dry steering stability performances and wear resistance and rolling resistance. From this viewpoint, many proposals have been made. For example, in JP-A-5-331316, a rubber 10 containing SBR containing 25 to 60% of bound styrene is disclosed.
It has been proposed to improve the wet performance during high speed running by using a composition in which 0 to 180 parts by weight of silica and 80 to 180 parts by weight of carbon black of N ₂ SA 80 m ² / g or more are blended in a tire tread. However, this compound has a problem that rolling resistance and abrasion resistance are poor.
Further, JP-A-5-51485 and JP-A-3-8404.
No. 9, JP-A-61-287802 and the like propose blending carbon black and silica with natural rubber or diene rubber such as SBR. With these blends, tire grip during running There is a problem that the characteristics and the rolling resistance cannot be compatible with each other. Furthermore, JP-A-3-23
In Japanese Patent No. 9737, 100 to 100 parts by weight of a rubber containing SBR having a specific ratio of styrene single chains and long chains with a bound styrene content of 20 to 50% and a glass transition temperature of −50 ° C. or higher, and silica fillers of 10 to 150 are used. It has been proposed to improve wet skid resistance by using a composition containing 1 part by weight and 0 to 100 parts by weight of carbon black for a tire tread, but this rubber composition cannot achieve dry steering stability at the same time. There's a problem.

[0003]

Therefore, the present invention eliminates the above-mentioned problems of the prior art, greatly improves wet braking performance and dry steering stability, and is excellent in wear resistance and rolling resistance characteristics. The present invention is intended to provide a pneumatic tire.

[0004]

According to the present invention, 80% by weight of emulsion-polymerized styrene polybutadiene rubber having a styrene content of 20 to 50% by weight, a butadiene content of cis of 15% or less, and a weight average molecular weight of 500,000 or more is used. Specific surface area of nitrogen (N ₂ S
A) is 140 m ² / g or more, 24M4DBP oil absorption is 9
30 to 70 parts by weight of carbon black and 10 to 40 parts by weight of carbon black having a half-value width (ΔDst) of the aggregate distribution of 50 ml or less at 0 ml / 100 g or more.
There is provided a pneumatic tire comprising a rubber composition having a total amount of carbon black and silica of 70 to 100 parts by weight in a cap tread, which is formed by mixing parts by weight.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the structure, operation and effect of the present invention will be described in detail. The structure of the pneumatic tire according to the present invention is not particularly limited, and not only a conventionally known pneumatic tire of any structure but also a pneumatic tire structure of various structures currently under development can be used. be able to. The point is that the cap tread portion may be made of the rubber composition having the above-mentioned configuration.

The rubber composition constituting the cap tread portion of the pneumatic tire according to the present invention has a styrene content of 20.
-50% by weight, preferably 20-40% by weight, and the cis content of the butadiene portion is 15% or less, preferably 5-15.
%, Weight average molecular weight of 500,000 or more, preferably 500,000 to
It contains a diene rubber containing 80% by weight or more, and preferably 90% by weight or more of 2 million emulsion-polymerized styrene-butadiene copolymer rubber (SBR). The type of diene rubber may be any diene rubber conventionally used for tire treads, such as natural rubber (N
R), polyisoprene rubber (IR), various polybutadiene rubbers (BR), various SBRs, and the like. These diene rubbers can be used in any blend. The use of such a specific emulsion-polymerized SBR is necessary for achieving both grip performance and abrasion resistance.

The rubber composition constituting the cap tread portion of the pneumatic tire according to the present invention is preferably tan.
The peak temperature of δ is -10 to -30 ° C, preferably -1.
A peak value of 0.6 or more at 5 to -25 ° C, preferably 0.
It is preferably 7 or more for improving dry and wet grip performance. A more preferable rubber composition is tan δ
Peak value / tan δ at 60 ° C. = 2 to 4.

The rubber composition constituting the cap tread portion of the pneumatic tire of the present invention further comprises, as an essential component,
It contains the aforementioned specific carbon black and silica.

Car used in the rubber composition according to the present invention
Bonblack has a nitrogen specific surface area (N ₂SA) is 140m
²/ G or more, preferably 140 to 200 m²/ G, 24
M4DBP oil absorption is 90ml / 100g or more, preferably
90-130ml / 100g, measured by centrifugal sedimentation method
The full width at half maximum (ΔDst) of the aggregate distribution is 50 mμ or less,
It is preferably 20 to 50 mμ, and the rubber composition contains rubber.
30 to 70 parts by weight (phr) per 100 parts by weight, preferably
40 to 70 phr, which is 70 in total with silica described below.
Add ~ 100 phr.

The silica used in the rubber composition according to the present invention is 10 to 40 phr, preferably 10 to 40 phr of any silica (white carbon) that can be used in rubber compounding.
Add 30 phr. Preferred silica has N ₂ SA of 100
Wet process silica of 400 m ² / g. The total amount of carbon and silica in the rubber composition according to the present invention is 70-70.
It should be 100 phr, preferably 75-95 phr, and further silica / carbon blacks (I) and (II)
The ratio is preferably 0.1 to 1.0. If the amount of silica is too small, it becomes difficult to obtain the effect of improving the wet performance and rolling resistance, which is the effect of silica, and if the amount of silica is too large, the wear resistance and dry performance may decrease. .

The rubber composition according to the present invention preferably further contains a silane coupling agent in an amount of 5 to 20% by weight based on the amount of silica, in order to strengthen the bond between the polymer and silica. desirable. Examples of such silane coupling agents include bis- (3-triethoxysilylpropyl) tetrasulfide, 3-trimethoxysilylpropylbenzothiazoletetrasulfide, γ-glycidoxypropyl-trimethoxysilane, γ-mercapto. Examples include propyl-trimethoxysilane and the like.

The rubber composition according to the present invention further comprises a silica compounding amount in order to prevent the vulcanization accelerator from being adsorbed on the surface OH groups of silica, prevent the vulcanization delay, and assist the dispersion of silica. It is preferable to use 1 to 15% by weight of the active agent in combination. Examples of such activators include glycols such as ethylene glycol, diethylene glycol and triethylene glycol.

The rubber composition according to the present invention is preferably
Rubber strength index is 130 × 10 ³ or more, more preferably 1
It is 40 × 10 ³ or more. Here, the rubber strength index can be calculated by the product of tensile strength (TB; kgf / cm ² ) and elongation (EB;%) obtained in a tensile test, that is, TB × EB.
By ensuring such a rubber strength index, wear resistance can be improved.

In addition to the above-mentioned essential and desired components, the rubber composition according to the present invention is generally blended with sulfur, vulcanization accelerators, antioxidants, fillers, softeners, plasticizers, etc. for tires. Various additives described above can be blended, and such a blend can be vulcanized by a general method to produce a tire tread. The amount of these additives may be a general amount. For example, the compounding amount of sulfur is rubber 1
It is preferable to use 1.0 part by weight or more per 00 parts by weight,
More preferably, it is 1.5 to 3.0 parts by weight.

[0015]

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 and Comparative Examples Each component was blended according to the blending content (parts by weight) shown in Table I, and the vulcanization accelerator and the raw material rubber excluding sulfur and the blending agent were 1.
After mixing with a 7 liter Banbury mixer for 5 minutes,
The mixture was kneaded with a vulcanization accelerator and sulfur with an 8-inch test kneading roll machine for 4 minutes to obtain a rubber composition. These rubber compositions were press-vulcanized at 160 ° C. for 20 minutes to prepare target test pieces, various tests were conducted, and their physical properties were measured. The physical properties of the obtained vulcanizate are as shown in Table 1.

[0016]

[Table 1]

[0017]

[Table 2]

(1) Blending component SBR-1 in Examples and Comparative Examples : emulsion polymerization SBR (37.5 phr oil extension, molecular weight Mw: 640,000) (styrene content: 24%, cis content: 9)
%) SBR-2: emulsion-polymerized SBR (37.5 phr oil extended, molecular weight Mw: 840,000) (styrene content: 38%, cis content: 1)
0%) SBR-3: emulsion-polymerized SBR (37.5 phr oil extension, molecular weight Mw: 910,000) (styrene content: 47%, cis content: 1)
0%) SBR-4: emulsion-polymerized SBR (non-oil extended, molecular weight Mw: 42)
10,000) (Styrene content: 24%, cis content: 8%) SBR-5: Solution polymerization SBR (non-oil extended) (Styrene content: 23%, vinyl content: 37%) SBR-6: Solution polymerization SBR (non-oil) Exhibition) (Styrene content: 21%, Vinyl content: 67%)

Carbon black-1: N ₂ SA = 142
m ² / g, 24M4DBP = 101 ml / 100 mg, ΔD
st = 48 mμ carbon black-2: N ₂ SA = 153 m ² / g, 2
4M4DBP = 100ml / 100mg, ΔDst = 53m
μ Carbon black-3: N ₂ SA = 111 m ² / g, 2
4M4DBP = 97 ml / 100 mg, ΔDst = 61 mμ

(Note) Method for measuring characteristics of carbon black (a) Nitrogen specific surface area (N ₂ SA) ASTM-D3037-78 "Standard Me.
hows of Treating Carbon
Black-Surface Area by Nitr
Measured according to the method of gen Adsorption. (B) 24M4DBP oil absorption measured according to ASTM-D-3493. (C) Full width at half maximum of aggregate distribution (ΔDst) Disc centrifuge (Joiice Loeb, UK)
(manufactured by Company I) and measured by the following method. That is, carbon black was precisely weighed, 20% by volume aqueous ethanol solution and a surfactant were added, and the carbon black concentration was 5 mg / 1.
A sample solution is prepared by ultrasonically dispersing so as to be 00 cc. Next, set the rotation speed of the disc centrifuge to 8
The spin solution (distilled water) (10 ml) was added to the disc centrifuge at 000 rpm, and then 0.5 ml of a buffer solution (20% by volume aqueous ethanol solution) was injected.
Then, 0.5 to 1.0 ml of the sample solution is added to this with a syringe to start centrifugal sedimentation, and an aggregate distribution curve converted by Stokes diameter is prepared by a photoprecipitation method. The distribution value of the aggregate at half the most frequent frequency (maximum absorbance) in the histogram is defined as the half-value width (ΔDst).

Silica: “Nipseal AQ” manufactured by Nippon Silica Co., Ltd. Silane coupling agent: “Si69” manufactured by Degussa Activator: Diethylene glycol Aromatic oil: “Process oil X-140” manufactured by Kyodo Petroleum Co., Ltd. Zinc flower: Positive Same chemical Co., Ltd. "Zinc flower No. 3" Stearic acid: Kao Soap Co., Ltd. "Lunac YA" Anti-aging agent: N-Phenyl-N '-(1,3-dimethyl) -p-phenylenediamine (Sumitomo Chemical Industry Co., Ltd.
"Antigen 6C" manufactured by Wax: "Sannock" manufactured by Ouchi Shinko Kagaku Co., Ltd. Sulfur: Oil-treated sulfur Vulcanization accelerator: N-tert-butyl-2-benzothiazolylsulfenamide (Ouchi Shinko Chemical Co., Ltd. ) "NOX CELLER NS-F")

(2) Performance Evaluation in Examples and Comparative Examples
Method tan δ Peak temperature and peak value These are values when measured using a viscoelasticity spectrometer (manufactured by Toyo Seiki Co., Ltd.) under conditions of initial strain of 10%, dynamic strain of ± 0.5%, and frequency of 20 Hz. Tensile strength (TB; kgf / cm ² ) and elongation (EB;%) are measured by conducting a tensile test according to the rubber strength index JIS K 6301.
Calculated product of the obtained TB and EB. Lambourn abrasion A Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) was used to measure the abrasion loss under a predetermined condition of a temperature of 20 ° C., and the value of Comparative Example 1 was set to 100 and displayed as an index. The larger the value, the better the wear resistance. Impact resilience According to JIS K 6301, the impact resilience at a temperature of 60 ° C. was measured. Dry steering stability Each tire (size 1) by a test driver on a dry road surface
95 / 60R14) feeling, comparative example 1
Was displayed as an index. The larger the value, the better the steering stability. Wet Braking Performance Running on a sprinkled asphalt road surface at an initial speed of 40 km / h (tire size: 195 / 60R14), the braking distance when braking was measured, and Comparative Example 1 was set to 100 and indicated as an index. The larger the value, the better the braking performance. Abrasion resistance Under the conditions of design normal load and air pressure specified in JATMA, after running 10,000 km on a dry road surface, the wear amount of each tire (size: 195 / 60R14) is an index for the wear amount of the tire of Comparative Example 1. Indicated. The larger the value, the better the wear resistance. The rolling resistance value at a rolling resistance speed of 80 km / h was measured (tire size: 195 / 60R14), and Comparative Example 1 was set as 100 and indicated as an index. The higher the value, the lower the rolling resistance value.

In Table I, Comparative Example 1 is a conventional typical cap compound formulation. On the other hand, Examples 1 to 7 according to the present invention are improved in dry steering stability, wet braking performance, wear resistance, and rolling resistance as compared with Comparative Example 1 which is a conventional typical example. Moreover, these are in a highly balanced state.

On the other hand, Comparative Examples 2 and 3 are different from Example 1 in that the carbon other than the regulation of the present invention is blended, so that the dry steering stability is deteriorated or the abrasion resistance is also deteriorated (Comparative Example 3). ) Do. Comparative Example 4 does not contain silica as compared with Example 1. In the example, the dry steering stability is reduced and the effect of improving wet braking performance is small. Comparative Example 5 is an example in which silica is blended in an amount exceeding the specified amount as compared with Example 1, and the dry steering stability is reduced. Comparative Example 6 is an example in which a polymer having a molecular weight of less than the specified value is blended, and the rubber strength index is lowered, the abrasion resistance is poor, and the dry steering stability cannot be improved. Dry Comparative Examples 7 and 8 are examples in which the peak temperature of tan δ is out of the specified range, and the dry steering stability and wear resistance are deteriorated. Comparative Example 9-
No. 12 is an example in which solution-polymerized SBR is combined, and the level of dry steering stability is low.

[0025]

As described above, according to the present invention, a polymer system and carbon / carbon material specific to the cap tread rubber are used.
By blending a silica-based material and defining the tan δ characteristic, the dry and wet performances are significantly improved, and a high-order balance with abrasion resistance and rolling resistance can be achieved.

To improve the grip performance of the tire,
High hysteresis loss of tread rubber, that is, high tan δ
Based on this, there are many conventional methods for increasing tan δ around 0 to 60 ° C. by blending a small particle diameter carbon that imparts high tan δ and blending several kinds of polymers. It has been taken. However, according to such a method, although the limit grip is particularly high on a dry road surface and the steering stability is reasonably good, it has not been possible to achieve compatibility with wet grip, wear resistance, or rolling resistance.
It was also found that the method of increasing tan δ at a relatively high temperature is good in the early stage of running, but the heat is gradually increased, the rubber is softened, and the steering stability is significantly reduced. Therefore, as a result of intensive studies to improve this, in the present invention, the combination of the specific polymer / filler system and the tan δ characteristic stabilizes the heat generation due to running, and the tan δ in the specific temperature range is high (the vibration frequency of the rubber during wear is high). Since it reaches several thousand Hz, tan δ at a low frequency, which is several tens of degrees lower than the actual rubber temperature, correlates with hysteresis loss, so if the temperature of the rubber is stable, t of the specific temperature range corresponding to it
The grip can be improved by increasing an δ), the steering stability can be improved, and it has succeeded in achieving compatibility with other performances.

Claims (3)

[Claims] 1. An emulsion-polymerized styrene polybutadiene rubber having a styrene content of 20 to 50% by weight, a butadiene content of cis of 15% or less, and a weight average molecular weight of 500,000 or more.
Nitrogen specific surface area (N ₂ SA) is 140 m ² / g or more, 24 M, based on 100 parts by weight of diene rubber containing 0 or more parts by weight.
4 DBP oil absorption is 90 ml / 100 g or more, and full width at half maximum (ΔDst) of aggregate distribution measured by centrifugal sedimentation method is 5
30 to 70 parts by weight of carbon black of 0 mμ or less and 10 to 40 parts by weight of silica are compounded, and a rubber composition in which the total amount of carbon black and silica is 70 to 100 parts by weight is used for a cap tread. tire. 2. The pneumatic tire according to claim 1, wherein the rubber composition has a tan δ peak temperature of −10 to −30 ° C. and a peak value of 0.6 or more. 3. The rubber strength index of the rubber composition is 130 × 1.
The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is 0 ³ or more.