JPH09226311A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extensively improve wet braking performance and dry steering stability and to make a pneumatic tire excellent in grip performance abrasion resistance and rolling resistance characteristics. SOLUTION: It is constituted by blending A parts by weight of carbon black of more than 140m<2> /g of (A) a nitrogen ratio surface area (N2 SA), more than 90ml/100g of 24M4DBP oil absorption and less than 50mμ of half value width (ΔDst) of aggregate distribution measured by a centrifugal precipitation method and B parts by weight of carbon black of 60-90m<2> /g of (B)N2 SA, more than 100ml/100g of 24M4DBP and more than 70μm of ΔDst against diene system rubber 100 parts by weight including more than 70 parts by weight of emulsion polymerized styrene-butadiene copolymerized rubber of 20-50weight% of styrene content and more than 500,000 of weight average molecular weight, and a rubber component of 70-100 weight of total quantity of A and B and A:B=3:1-1:3 is used for a cap tread.

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 rubber composition containing a specific polymer and carbon black as a cap tread rubber, tan δ characteristics are defined and dry and wet performances are improved. The present invention relates to a pneumatic tire that is significantly 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 point of view, many proposals have been made by specifying the carbon black and the rubber component to be blended. For example, in Japanese Patent Application Nos. 1-164602 and 1-315439, it is described that a specific SAF grade carbon black is blended in a high amount to improve the steering stability. There is a problem of insufficient resistance. Further, JP-A-63-225639 and JP-A-4-274901 describe that the wear performance is improved by blending a specific HAF grade carbon black. However, this blend has a grip performance. There is a problem that it is not enough. Further, JP-A-59-4631 describes that a blend of a high structure carbon black and a low structure carbon black is blended to improve rolling resistance, but this blend has sufficient grip performance. There is a problem that is not. Furthermore, JP-A-62
In Japanese Patent Publication No. 156145, an S-SBR / NR system is used.
It has been proposed to improve the wear resistance by setting the nδ peak to -50 to -30 ° C, but this formulation has a problem that grip performance is not sufficient. Further, JP-A-7-41602 describes that a rubber material having desirable characteristics can be obtained by blending a blend of a large particle size carbon black and a small particle size carbon black, but it is not always appropriate. It cannot be said to be a carbon black blend system.

[0003]

As described above, no technique has hitherto been known that achieves a high-order balance of grip performance, abrasion resistance and rolling resistance by appropriately blending a polymer / carbon system. Therefore, the present invention eliminates the problems of the prior art, the grip performance on wet and dry roads is significantly improved, and provides a pneumatic tire having excellent wear resistance and rolling resistance characteristics. To aim.

[0004]

According to the present invention, 100 parts by weight of a diene rubber containing 70 parts by weight or more of an emulsion-polymerized styrene-butadiene copolymer rubber having a styrene content of 20 to 50% by weight and a weight average molecular weight of 500,000 or more. (A) nitrogen specific surface area (N ₂ SA) is 140 m ² / g or more, 24 M
4 DBP oil absorption is 90 ml / 100 g or more, half-value width (ΔDst) of aggregate distribution measured by centrifugal sedimentation method is 50
Carbon black of mμ or less is A weight part and (B)
N ₂ SA is 60 to 90 m ² / g, 24M4DBP is 10
A rubber composition comprising 0 parts by weight / 100 g or more of carbon black having a ΔDst of 70 mμ or more and B parts by weight, and the total amount of A and B is 70 to 100 parts by weight and A: B = 3: 1 to 1: 3. Provided is a pneumatic tire using an object as a cap tread.

[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 cap tread portion of the pneumatic tire according to the present invention contains a specific polymer (rubber component) in the cap tread of the pneumatic tire in order to balance dry and wet performance with wear resistance and rolling resistance. Add specific carbon.

The polymer compounded in the rubber composition used in the cap tread portion of the pneumatic tire of the present invention has a styrene content of 20 to 50% by weight, preferably 20 to 40.
% By weight, weight average molecular weight of 500,000 or more, preferably 6
Emulsion-polymerized styrene-butadiene copolymer rubber (S
BR) is a diene rubber containing 70 parts by weight or more, preferably 80 parts by weight or more (for example, natural rubber, polybutadiene rubber, polyisoprene rubber, etc.), and these can be used in any blend. Use of such a rubber component is necessary for achieving both grip performance and abrasion resistance, and it is particularly preferable to use BR, preferably BR having 90% or more cis 1,4 bonds in combination, because the effect is large.

The carbon black blended in the rubber composition used for the cap tread portion of the pneumatic tire of the present invention has (A) N ₂ SA of 140 m ² / g or more, preferably 140 to ²⁰⁰ m ² / g, 24M4DBP oil absorption (B) 90ml / 100g or more, preferably 90-130
ΔDst is 50 mμ or less at ml / 100 g, preferably 3
0 to 50 mμ of carbon black Aphr (parts by weight per 100 parts by weight of rubber) and (B) N ₂ SA of 60 to 90 m
² / g, preferably 70 to 90 m ² / g, 24M4DB
P oil absorption is 100ml / 100g or more, preferably 100
˜140 ml / 100 g, and ΔDst is 70 mμ or more, preferably 80 to 130 mμ of carbon black Bphr is added, and the total of A and B is 70 to 100 phr and A: B.
= 3: 1 to 1: 3, preferably 2: 1 to 1: 2, a combination of specific carbon blacks A and B is used. By such a blend of the specific SAF grade carbon black and HAF grade carbon black, the grip performance, abrasion resistance and rolling resistance of the rubber composition are highly balanced.

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
The peak value / tan δ value ratio at 60 ° C. is 2 to 4.

The rubber composition according to the present invention contains, in addition to the above essential components, sulfur, a vulcanization accelerator, an antioxidant, a filler,
Various additives generally used for tires, such as softening agents and plasticizers, can be added, and the compound 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 preferably 1.0 part by weight or more per 100 parts by weight of rubber, and 1.0 to 3.
More preferably, it is 0 part by weight.

[0011]

EXAMPLES The present invention will be further described with reference to the following examples, but it goes without saying that the scope of the present invention is not limited to these examples. Examples 1 to 7 and Comparative Examples 1 to 13 The respective components were blended according to the blending content (parts by weight) shown in Table I, and the vulcanization accelerator and the raw material rubber and compounding agent excluding sulfur 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 shown in Table I.

The compounding agents used in the following comparative examples and examples are as follows. SBR-1--Emulsion polymerization SBR (37.5 phr oil extended, molecular weight Mw: 640,000, styrene content: 24%, vinyl content: 1
5%) SBR-2--Emulsion polymerized SBR (37.5 phr oil extended, molecular weight Mw: 840,000, styrene content: 38%, vinyl content: 1
4%) SBR-3--Emulsion polymerization SBR (37.5 phr oil extension, molecular weight Mw: 910,000, styrene content: 47%, vinyl content: 1
3%) SBR-4 --- solution polymerized SBR (non-oil extended, styrene content:
21%, vinyl content: 67%) BR--cis content: 98%, 37.5 phr oil extension

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 = 84 m ² / g, 24
M4DBP = 107 ml / 100 mg, ΔDst = 85 mμ Carbon black-3-N ₂ SA = 153 m ² / g, 2
4M4DBP = 100ml / 100mg, ΔDst = 53m
μ Carbon black-4-N ₂ SA = 111 m ² / g, 2
4M4DBP = 97 ml / 100 mg, ΔDst = 61 mμ Carbon black-5--N ₂ SA = 106 m ² / g, 2
4M4DBP = 101ml / 100mg, ΔDst = 81m
μ Carbon black-6--N ₂ SA = 92 m ² / g, 24
M4DBP = 101 ml / 100 mg, ΔDst = 68 mμ Carbon black-7--N ₂ SA = 44 m ² / g, 24
M4DBP = 75 ml / 100 mg, ΔDst = 140 mμ

Aromatic Oil--Kyodo Oil Co., Ltd. "Process Oil X-140" Zinc Hua--Shodo Chemical Co., Ltd. "Zinc Hua No.3" Stearic Acid--Kao Soap Co., Ltd. "Lunack YA""Anti-aging agent-N-phenyl-N '-(1,3-dimethyl) -p-phenylenediamine (" Antigen 6C "manufactured by Sumitomo Chemical Co., Ltd.) Wax-manufactured by Ouchi Shinko Chemical Co., Ltd. Sannock "Sulfur--Oil-treated Sulfur Vulcanization Accelerator--N-tert-butyl-2-benzothiazolylsulfenamide (Onoshin Shinko Kagaku Co., Ltd.“ Nocceller-NS-F ”)

The performance evaluation methods used in the following comparative examples and examples are as follows. (1) Tan δ peak temperature and peak value With a viscoelasticity spectrometer (manufactured by Toyo Seiki Co., Ltd.), values measured under conditions of initial strain 10%, dynamic strain ± 0.5%, and frequency 20 Hz. is there. (2) 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 Comparative Example 1 was set to 100 and indicated as an index. The larger the value, the better the wear resistance. (3) Impact resilience The impact resilience at a temperature of 60 ° C. was measured according to JIS K 6301.

The following tests are for tire size 195 / 60R
This was done using 14 tires. (4) Dry steering stability The feeling of each tire by a test driver was scored on a dry road surface, and the comparative example 1 was set to 100 and indexed.
The larger the numerical value, the better the steering stability. (5) Wet braking performance Running on an asphalt road surface with water removed at an initial speed of 40 km / h,
The braking distance when braking was measured, and the comparative example 1 was set to 100 and displayed as an index. The larger the numerical value, the better the braking performance. (6) Abrasion resistance The tire wear amount of each tire was shown as an index relative to the tire wear amount of Comparative Example 1 after traveling 10,000 km on a dry road surface under the conditions of design normal load and air pressure specified in JATMA. The larger the value, the better the wear resistance. (7) Rolling resistance The rolling resistance value at a speed of 80 km / h was measured, and the comparative example 1 was set as 100 and displayed as an index. The larger the value, the lower the rolling resistance value.

The methods for measuring the characteristics of the carbon blacks used in the comparative examples and examples are as follows. (A) Nitrogen Specific Surface Area (N ₂ SA) ASTM-D3037-78 Method C “Standard Methods of Treati
ng Carbon Black-Surface Area by Nitrogen Adsorpti
(b) 24M4DBP oil absorption amount according to ASTM-D-3493. (c) Full width at half maximum (ΔDst) of flocculation resistance distribution disc centrifuge (British Loewe )
(manufactured by Bl Inc.) is measured by the following method. That is, carbon black is precisely weighed, 20% by volume aqueous ethanol solution and a surfactant are added, and the carbon black concentration is 5 mg /
A sample solution is prepared by ultrasonically dispersing to 100 cc. Next, the rotational speed of the disc centrifuge is set to 8000 rpm, 10 ml of the spin solution (distilled water) is added to the disc centrifuge, and then 0.5 ml of the buffer solution (20% by volume aqueous ethanol solution) is 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).

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

As shown in Table I, Comparative Example 1 is a typical example of a conventional cap compound, and the following Examples and Comparative Examples were evaluated using this result as a standard. As shown in Table I, Examples 1 to 7 according to the present invention have clearly improved steering stability, wet performance, wear resistance, and rolling resistance. On the other hand, Comparative Examples 2 and 3 are Example 1
On the other hand, since the blending ratio of the specific carbon black is out of the regulation of the present invention, steering stability or rolling resistance is lowered. Comparative Examples 4 and 5 are different from Example 1 in that the blending of carbon black is not used, and therefore the steering stability is not improved. Since Comparative Examples 6 to 9 are blended with carbon black which is out of the specification with respect to Example 1, the respective performances are not balanced. Comparative Example 10 is a system in which a non-specified carbon black is blended and the steering stability cannot be improved.
In No. 13, as compared with Example 1, the tan δ characteristic or the polymer system is out of the specified range, and therefore the steering stability cannot be improved.

Claims (2)

[Claims] 1. A nitrogen specific surface area (A) relative to 100 parts by weight of a diene rubber containing 70 parts by weight or more of an emulsion-polymerized styrene-butadiene copolymer rubber having a styrene content of 20 to 50% by weight and a weight average molecular weight of 500,000 or more. (N ₂ SA) is 140
m ² / g or more, 24M4DBP oil absorption is 90 ml / 100
g of carbon black having a full width at half maximum (ΔDst) of 50 mμ or less of the aggregate distribution measured by the centrifugal sedimentation method is A weight part and (B) N ₂ SA is 60 to 90 m ² / g,
24M4DBP is 100ml / 100g or more, and ΔDst is 70mμ or more, and is made by mixing B parts by weight. The total amount of A and B is 70 to 100 parts by weight and A: B.
= 3: 1 to 1: 3, a pneumatic tire using a rubber composition for a cap tread. 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.