JPH09255814A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for tire tread capable of keeping low exothermic properties and improving wet skid function without decreasing working properties and abrasion resistance. SOLUTION: This rubber composition comprises 100 pts.wt. of a rubber component containing 30-40wt.% of styrene component blended with 5-30 pts.wt. of powdery aluminum hydroxide and/or clay and 30-100 pts.wt. of carbon black having >=65m<2> /g nitrogen adsorption specific area (N2 SA) and >=90cm<3> /100g dibutyl phthalate oil absorption (DBP).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a tire tread, and more specifically, it maintains low heat generation performance without lowering workability and wear resistance, and further has braking performance on a wet road surface and steering performance. The present invention relates to a rubber composition having greatly improved stability (hereinafter referred to as "wet skid performance").

[0002]

2. Description of the Related Art Conventionally, in a rubber composition for a tire tread, as means for improving the wet skid performance, a high content of silica is compounded, a glass transition temperature (Tg) of the rubber, that is, a loss tangent (tan δ at 0 ° C.).
It is known to increase the value), or to make the particle size of carbon black finer and mix it in a highly filled state.

However, a rubber composition for a tire tread containing a high silica content has a problem in workability (workability), and a rubber composition having a high Tg deteriorates low-temperature performance and rolling resistance (rolling resistance). ,Less than,
There is a problem in that the "RR") becomes high, and in the case where the carbon black has a fine particle size and is highly filled, the RR becomes high.

As a technique intended to solve these problems or a technique similar thereto, for example, a rubber composition for a tire tread in which wet skid performance is improved by devising a special silica and kneading, and a method for producing the same. (European Patent No. 501227), low-temperature plasticizer 1 having a freezing point of -48 ° C or lower with respect to 100 parts by weight of natural rubber and / or diene-based synthetic rubber.
Improvement of ice skid performance by blending 0 to 80 parts by weight with 5 to 40 parts by weight of silicon carbide, silicon nitride, aluminum oxide, silica stone having an average particle size of 0.1 to 1 mm or a mixture thereof. Rubber composition for tire tread (Japanese Patent Application Laid-Open No. 2-135241), which has an effect on the following effects: Low-temperature plasticizer 1 having a freezing point of −40 ° C. or lower with respect to 100 parts by weight of natural rubber and / or diene-based synthetic rubber
A rubber composition for a tire tread having a high friction property on ice, which is obtained by using a combination of 0 to 80 parts by weight and 5 to 45 parts by weight of alumina having an average particle diameter of 0.01 to 0.5 mm (Japanese Patent Application Laid-Open No. 2000-242242). JP-A-60-147450), and the like are known.

[0005]

However, the rubber composition for tire tread described in the above-mentioned European Patent No. 501227 has a problem in workability (workability), and the above-mentioned JP-A-2-135241. The rubber composition for a tire tread described in No. 1 has a problem in wear resistance, and the rubber composition for a tire tread described in JP-A-60-147450 has wear resistance and fracture resistance. There was a problem.

Therefore, in the above conventional technique, at least one of workability, wear resistance, and low heat buildup is sacrificed in order to improve wet skid performance and the like. At present, there is no rubber composition for a tire tread that satisfies both the wet skid performance and the wet skid performance.

Therefore, an object of the present invention is to provide a rubber composition for a tire tread capable of maintaining low heat build-up and improving wet skid performance without lowering workability and wear resistance.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems of the prior art, the present inventors have made a polymer having a styrene content in a specific range as a rubber component, and added a specific inorganic compound powder thereto. The inventors have found that the rubber composition for a tire tread of the above purpose can be obtained by blending a specific amount of carbon black and carbon black, and have completed the present invention.

That is, in the rubber composition for tire tread of the present invention, aluminum hydroxide (Al (OH) ₃ ) and / or aluminum hydroxide (Al (OH) ₃ ) and / or 100 parts by weight of the rubber component having a styrene content of 30 to 40% by weight is used. 5 to 30 parts by weight of clay powder (hereinafter abbreviated as "inorganic compound powder"), 65 m
² / g or more nitrogen adsorption specific surface area (N ₂ SA) and 90
cm ^3/100 g or more dibutyl phthalate oil absorption (D
30 to 100 parts by weight of carbon black (BP) is blended.

It is preferable that the silane coupling agent is added in an amount of 5 to 15% by weight with respect to the amount of the inorganic compound powder compounded.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber material used in the rubber composition of the present invention is a styrene-butadiene rubber (SBR), a natural rubber (NR) or a natural rubber (NR) if the styrene content is in the range of 30 to 40% by weight. Butadiene rubber (BR) can be blended. If the content of the styrene component is less than 30% by weight, wet skid performance is deteriorated, while 4
If it exceeds 0% by weight, the RR becomes high and the abrasion resistance decreases, which is not preferable.

The amount of the inorganic compound powder compounded in the rubber composition of the present invention is 5 to 30 parts by weight, preferably 10 to 25 parts by weight, based on 100 parts by weight of the rubber component. If the content of the inorganic compound powder is less than 5 parts by weight, wet skid performance cannot be improved, while if it exceeds 30 parts by weight, abrasion resistance is adversely affected, which is not preferable.

Further, as the carbon black to be blended with the rubber composition of the present invention, a nitrogen adsorption specific surface area (N ₂ S
A) is 65 m ² / g or more, preferably 70 to 145 m ²
/ G, more preferably 100 to 20 for general purpose tires
0m ² / g, 150-240m ² / g for high performance tires
It is. When N ₂ SA is less than 65 m ² / g, sufficient abrasion resistance cannot be obtained when the above inorganic compound powder is mixed, which is not preferable.

Further, dibutyl phthalate absorption of the carbon black (DBP) is 90cm ^3/100 g or more, preferably 100~180cm ³ / 100g, more preferably, in the general-purpose tires 100~160cm ³ /
100g, is a high-performance tire 110~170cm ^3/1
00 g. DBP is not taken sufficient abrasion resistance when 90cm ³ / inorganic compound powder is less than 100g is mixed, is not preferred.

The nitrogen adsorption specific surface area (N ₂ S
A) was determined according to the ASTM D4820-93 method, and DBP was determined according to the ASTM D2414-93 method.

The amount of the carbon black compounded is 30 to 100 parts by weight based on 100 parts by weight of the rubber component.
Preferably 35 to 95 parts by weight, more preferably 40 to
90 parts by weight. If the blending amount of carbon black is less than 30 parts by weight, abrasion resistance becomes insufficient, while 10
If it exceeds 0 parts by weight, workability (workability) deteriorates, which is not preferable.

Furthermore, in the rubber composition of the present invention, in order to improve the chemical adhesion between the inorganic compound powder and the rubber matrix, silane coupling is performed with respect to the compounding amount of the inorganic compound powder. It is preferable to add 5 to 15% by weight of the agent. If the amount added is less than 5% by weight, sufficient adhesive force cannot be obtained, while if it exceeds 15% by weight, the rubber elastic modulus increases and the cost also significantly increases, which is not preferable.

Next, examples of silane coupling agents that can be used in the present invention are as follows. Bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3- Mecaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 3
-Nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane,
2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide , 3-trimethoxysilylpropyl methacrylate monosulfide, etc., bis (3-triethoxysilylpropyl) tetrasulfide, 3-trimethoxysilylpropyl benzene. Such as thiazole tetrasulfide are preferable.

In the rubber composition of the present invention, a vulcanizing agent, a vulcanization accelerator, a softening agent, an antiaging agent and the like which are usually used, are properly blended in addition to the above-mentioned compounding agents.

[0020]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. Various rubber compositions were prepared according to the formulations (parts by weight) shown in Tables 1 and 2 below. The following performance evaluation test was performed on the obtained rubber composition.

(A) Wet skid performance The test rubber composition was used as a tread rubber and size 19 was used.
A test tire of 5/65 R14 was produced. The tire was mounted on a trailer, and a trailer test of the tire by the method of US UTQGS was conducted under the following conditions. The tire was rotated on a wet asphalt road surface, the rotation of the tire was slowed down, and the relationship between the slip ratio and the friction coefficient μ was measured. The peak μ was shown as an index with the data of Comparative Example 1 as 100. The higher the value, the better the result. (B) Abrasion resistance A Lambourn abrasion test was performed to examine the volume loss under the measurement conditions of a slip ratio of 50% and room temperature.
The index was set to 0. The higher the value, the better the result. (C) Low exothermicity The impact resilience was measured, and the value (%) was expressed as an index with the data of Comparative Example 1 as 100. The higher the value, the better the result. (D) Workability The Mooney value was obtained according to the Mooney viscosity measurement method defined in JIS K 6300, and the data of Comparative Example 1 was set to 100.
Exponential notation. The smaller the number, the better the result.

[0022]

[Table 1]

[0023]

[Table 2] 1) Styrene content: 23.5% by weight, Tg: -56 ° C
(Japan Synthetic Rubber Co., Ltd.) 2) Styrene content: 35% by weight, Tg: -44 ° C (Japan Synthetic Rubber Co., Ltd.) 3) Styrene content: 40% by weight, Tg: -40 ° C (Japan Synthetic Rubber) 4) Styrene content: 23.5% by weight, Tg: -56 ° C
(Nippon Synthetic Rubber Co., Ltd.) 5) Carbon black N234 (N ₂ SA: 126 m ^{2
/ G, DBP: 125cm 3 /} 100g) 6) N- (1,3- dimethylbutyl)-N'-phenyl -p- phenylenediamine 7) Degussa Co. Silane coupling agent Si69
(Bis (3-triethoxysilylpropyl) tetrasulfide)

As is clear from Table 1 above, the rubber compositions of the present invention in each of the examples have improved workability and wear resistance, improved low heat buildup, and have a wet skid performance. Significantly improved.

On the other hand, in Comparative Example 2, since the styrene content of the rubber component is small, the improvement in wet skid performance is small. Further, in Comparative Example 3, silica was used instead of the inorganic compound powder, but in this case, the processability was low,
There is also little improvement in wet skid performance. Further, in Comparative Example 4, the Tg of the polymer was increased as compared with Comparative Example 1, and although this improved wet skid performance, wear resistance and low heat generation performance were reduced. Furthermore, in Comparative Example 5, the effect of improving wet skid performance is not observed.

[0026]

As described above, in the rubber composition for a tire tread of the present invention, it is possible to significantly improve low heat generation performance and wet skid performance without lowering workability and wear resistance. You can

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area C08K 5/54 KDV C08K 5/54 KDV

Claims (2)

[Claims] 1. A styrene component content of 30 to 40% by weight.
5 to 30 parts by weight of aluminum hydroxide and / or clay powder, and 65 m
² / g or more nitrogen adsorption specific surface area (N ₂ SA) and 90c
m ^3/100 g or more dibutyl phthalate oil absorption (DB
A rubber composition for a tire tread, which comprises 30 to 100 parts by weight of carbon black of P). 2. The rubber composition for a tire tread according to claim 1, wherein a silane coupling agent is added in an amount of 5 to 15% by weight based on the amount of the aluminum hydroxide and / or clay blended.