JP2002322318A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for a tire tread excellent in grip properties and abrasion resistance. SOLUTION: This rubber composition for the tire tread comprises 100 pts.wt. of a rubber component, 50-140 pts.wt. of silica, 30-70 pts.wt. of an oil, and 3-20 wt.% per silica of a silane coupling agent, wherein, when the weight of silica per 100 pts.wt. of the rubber component is (a) pts.wt., the crosslinking point density ρ% is expressed by the formula: ρ>=-0.5×(a)+270 (1).

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 particularly to a rubber composition for a tire tread having both grip performance and abrasion resistance.

[0002]

2. Description of the Related Art Tire rubber used for tire tread rubber, particularly high-performance tires used for high-performance passenger cars and motorcycles, and racing tires used for racing vehicles, has excellent braking performance during running. Traction performance and grip performance during cornering are required.

A conventional tread rubber uses a styrene-butadiene copolymer rubber (SBR) having a high styrene component content in order to satisfy these performances and to increase a friction coefficient generated between a road surface and a tread surface. A method and a method of highly filling a filler or a softener have been adopted.

[0004] However, it has been difficult to achieve both grip performance and abrasion resistance by these means.

[0005] When SBR having a high styrene component content is used, grip performance is improved, but if a large force is applied to the tread surface during cornering, abrasion wear occurs due to repeated large deformation. The greater the force applied to the rubber and the softer the rubber, the greater the deformation. Abrasion that occurs in a wave-like manner in the vertical direction due to continuous deformation in a certain direction is called abrasion wear. The greater the spacing and depth of the waves,
Not only does the appearance deteriorate, but the contact area between the rubber and the road surface is reduced, and performance is reduced.

[0006] Even when the amount of the filler and the softening agent is increased, it is difficult to achieve both the grip performance and the wear resistance performance.
That is, although a low elastic modulus and a high tan δ were achieved and the grip performance could be improved, the elastic modulus at 300% elongation also decreased. Rubber having a low elastic modulus in the strain region of large deformation tends to cause abrasion wear, and it is known that there is a correlation between the elastic modulus at 300% elongation measured by a tensile test and the interval between waves of abrasion wear.

[0007]

An object of the present invention is to provide a rubber composition having a high elastic modulus in a large deformation region and a high tan δ /
It is an object of the present invention to provide a rubber composition for a tire which is excellent in grip performance and abrasion resistance performance while satisfying both (elastic modulus in a region where distortion is small).

[0008]

According to the present invention, there is provided a rubber component comprising:
0 parts by weight, silica 50 to 140 parts by weight, oil 30 to 7
In a rubber composition containing 0 parts by weight and a silane coupling agent in an amount of 3 to 20% by weight based on silica, when the weight of silica relative to 100 parts by weight of the rubber component is a part by weight, the crosslinking point density ρ% Relates to a rubber composition for a tire tread that satisfies the formula: ρ ≧ −0.5 × a + 270 (1).

The rubber composition further comprises a rubber component 100
It is preferable that carbon black is contained in an amount of 5 to 70 parts by weight with respect to parts by weight, and the added amounts thereof are 50 to 95% by weight and 5 to 50% by weight, respectively, based on the total amount of silica and carbon black.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition of the present invention contains a rubber component, silica, oil and a silane coupling agent, and can further contain carbon black.

Examples of the rubber component used in the present invention include diene rubbers such as SBR, natural rubber, isobutylene rubber, acrylonitrilobutadiene rubber, butyl rubber, and p-methylstyrene / isobutylene copolymer. Can be used alone or in any combination.

When SBR is used as the rubber component, SB
The bound styrene content of R is preferably 15 to 60% by weight. If the amount of bound styrene is less than 15% by weight, sufficient grip performance tends not to be obtained, and if it exceeds 60% by weight, abrasion resistance tends to decrease.

As the silica, those conventionally used in the field of tires can be used without particular limitation. The nitrogen adsorption specific surface area of silica is 100 to 300
It is preferably m ² / g. Further, from the viewpoint of reinforcing properties, the nitrogen adsorption specific surface area is desirably 100 to 200 m ² / g.

As the carbon black, those conventionally used in the field of tires can be used without particular limitation. Nitrogen adsorption specific surface area of carbon black is preferably 70~300m ² / g. When the nitrogen adsorption specific surface area is less than 70 m ² / g, the effect of improving dispersibility and the effect of reinforcing tend to be small, and 300 m ² / g.
If the ratio exceeds the above range, dispersibility tends to decrease, heat generation increases, and abrasion resistance tends to decrease.

Examples of the carbon black include, for example, HAF, ISAF, SAF and the like.

The amount of the silica is 50 to 140 parts by weight based on 100 parts by weight of the rubber component. If the compounding amount of silica is less than 50 parts by weight, it is difficult to obtain a reinforcing effect.
If it exceeds 40 parts by weight, the dispersibility decreases, and the abrasion resistance decreases.

When compounding carbon black,
The amount of silica is preferably 50 to 95% by weight based on the total amount of silica and carbon black. If the amount of silica is less than 50% by weight, sufficient grip performance and abrasion resistance tend not to be obtained.

When the carbon black is compounded, the compounding amount is 5 parts by weight with respect to 100 parts by weight of the rubber component.
It is preferably from 70 to 70 parts by weight. If the amount of the carbon black exceeds 70 parts by weight, the workability tends to decrease, and the dispersibility tends to decrease.

Further, the compounding amount of carbon black is 5 to 50 with respect to the total amount of silica and carbon black.
% By weight. If the amount of the carbon black exceeds 50% by weight, the desired grip performance and wear resistance tend not to be obtained.

As the oil, paraffin-based process oil, aroma-based process oil, naphthene-based process oil and the like can be used. These can be used alone or in any combination.

The amount of the oil is 30 to 70 parts by weight based on 100 parts by weight of the rubber component. 3 oils mixed
If the amount is less than 0 parts by weight, sufficient grip performance cannot be obtained.
If the amount is more than the weight part, the abrasion resistance performance decreases.

As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used. Specifically, sulfide-based, mercapto-based, vinyl-based, amino-based, glycidoxy-based, nitro-based, and chloro-based silane coupling agents can be used.

Examples of the sulfide-based silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, and bis (3-trimethoxysilylpropyl) tetrasulfide. (2-trimethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (3- Trimethoxysilylpropyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxy Silylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyltetrasulfide, 3-triethoxysilylpropylbenzothiazole Examples thereof include tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, and 3-trimethoxysilylpropyl methacrylate monosulfide.

Examples of the mercapto silane coupling agent include 3-mercaptopropyltrimethoxysilane,
-Mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane and the like.

Examples of the vinyl silane coupling agent include vinyl triethoxy silane and vinyl trimethoxy silane.

Examples of the amino-based silane coupling agent include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, and 3- (2-aminoethyl ) Aminopropyltrimethoxysilane and the like.

As glycidoxy silane coupling agents, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ
-Glycidoxypropylmethyldiethoxysilane, γ-
Glycidoxypropylmethyldimethoxysilane and the like can be mentioned.

Examples of the nitro silane coupling agent include 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane.

Examples of the chlorosilane coupling agent include 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane.

Of these, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, and 3-mercaptopropyltrimethoxysilane are considered to be both effective in adding the coupling agent and cost. Etc. are preferably used. The silane coupling agent may be used alone or in combination of two or more.

The amount of the silane coupling agent is 3 to 20% by weight based on the silica. If the amount of the silane coupling agent is less than 3% by weight, the effect of the silane coupling agent cannot be sufficiently obtained. If the amount exceeds 20% by weight, the cost is increased but the effect corresponding thereto cannot be obtained.

In the rubber composition of the present invention, in addition to the above components, for example, vulcanization aids such as stearic acid and zinc oxide, vulcanizing agents such as sulfur, vulcanization accelerators, waxes, antioxidants, And the like.

When sulfur is compounded as a vulcanizing agent, the compounding amount of sulfur is 0.1 to 1 with respect to 100 parts by weight of the rubber component.
It is preferably 0 parts by weight.

The rubber composition of the present invention can be obtained by kneading the above components with a Banbury mixer, kneader or the like. The kneading temperature at this time is 130 to 180 ° C.
It is preferable that If the kneading temperature is less than 130 ° C., the silica and the silane coupling agent tend not to react sufficiently. If the kneading temperature exceeds 180 ° C., the crosslinking reaction is accelerated by sulfur atoms and gelation occurs, and the rubber skin tends to be damaged. . The kneading time is preferably 1 to 20 minutes. If the kneading temperature is less than 1 minute, the reaction between the silica and the silane coupling agent tends to be insufficient, and if it exceeds 20 minutes, the viscosity tends to increase too much.

When a vulcanizing agent and a vulcanization accelerator are blended, they are added after the above-mentioned kneading step, kneaded with an open roll, a Banbury mixer, a kneader or the like, and then vulcanized. The kneading temperature at this time is 120
It is preferable that the temperature is not higher than ° C. The kneading temperature may be lower than the vulcanization temperature in view of the dispersibility of the vulcanizing agent and the fact that the rubber does not burn. The temperature below the vulcanization temperature depends on the type and size of the product, but is usually 80 to 120 ° C.
It is.

The crosslinking point density ρ% of the rubber composition of the present invention is:
When the weight of silica relative to 100 parts by weight of the rubber component is a part by weight, it is necessary to satisfy the formula (1). If the crosslinking point density is too high despite the low weight of silica, the desired grip performance and wear resistance cannot be obtained. ρ ≧ −0.5 × a + 270 (1)

Here, the crosslinking point density is measured by the following method. The vulcanized rubber composition is cut into a flake shape of 20 mm in length × 20 mm in width × 2 mm in thickness to obtain a sample. After swelling the sample (Wd) by immersing it in toluene for 24 hours, the weight (Ws) of the swollen sample is measured.
From the measured Wd and Ws, the weight change rate ΔW% (ΔW =
(Ws−Wd) / Ws × 100) is obtained. The weight change rate is a general index for evaluating the crosslinking point density of the vulcanized rubber, and it is known that the larger the weight change rate, the lower the crosslinking point density. That is, there is a relationship like the equation (2) between the weight change rate and the crosslinking point density. By substituting the obtained weight change rate ΔW% into the equation (2), the crosslinking point density ρ% is calculated. You can ask. ρ (%) = ΔW% (2)

The rubber composition of the present invention can increase tanD / (elastic modulus in a region where strain is small) without decreasing the elastic modulus at 300% elongation, and is used in a tire tread for grip performance. And abrasion resistance performance can be satisfied.

[0039]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

Examples 1 to 3 and Comparative Examples 1 to 4 (Materials) SBR: Toughden 3330 (30% bound styrene) manufactured by Asahi Kasei Kogyo Co., Ltd. SAF carbon: Diamond Black A manufactured by Mitsubishi Chemical Corporation
(Nitrogen adsorption specific surface area 142 m ² / g, DBP oil absorption 1
Wax: Sannoc N manufactured by Ouchi Kosan Chemical Industry Co., Ltd. Antioxidant: Santoflex 13 manufactured by Flexis Co., Ltd. Stearic acid: Tung Zinhua manufactured by NOF Corporation: manufactured by Mitsui Kinzoku Mining Co., Ltd. Sulfur: powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator NS: Noxeller NS (N-tert-butyl-2benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfuric accelerator DPG: Soxeal D (N, N'-diphenylguanidine) manufactured by Sumitomo Chemical Co., Ltd. Aromatic oil: Process X-260 manufactured by Japan Energy Silane coupling agent: Si-69 manufactured by Degussa bis (3-triethoxysilylpropyl) tetrasulfide) silica: Degussa Ultra Jill VN3 (nitrogen adsorption specific surface area 210 m ² g)

(Production method) According to the composition shown in Table 1, B
In an R type Banbury mixer, materials other than sulfur and the vulcanization accelerator are kneaded with the base for about 3 minutes at a discharge temperature of 145 ° C.,
The obtained rubber composition, sulfur and a vulcanization accelerator were kneaded with an open roll for about 5 minutes to prepare a sheet. The prepared sheet was vulcanized at 170 ° C. for 12 minutes in a predetermined mold, and the following experiment was performed.

(Crosslinking Point Density) A sheet was cut into a flake having a size of 20 mm long × 20 mm wide × 2 mm thick to obtain a sample. After swelling the sample by immersing it in toluene for 24 hours, the weight of the swollen sample was measured, and the crosslink point density was determined from the weight change at this time. The larger the change in weight, the lower the density of cross-linking points.

(Tensile test) JIS tensile test method K
Based on 6251, a test was performed on a sample cut out into dumbbell No. 3. The measured stress (M300) at 300% elongation was expressed as an index, with the case of Comparative Example 1 taken as 100. The larger the index, the better the abrasion resistance.

(Hardness) The hardness was measured with a JIS-A hardness meter at 25 ° C. in an atmosphere.

(Viscoelasticity) Using a viscoelasticity spectrometer manufactured by Iwamoto Manufacturing Co., Ltd., the initial strain was set to 10% and 50%.
The viscoelasticity when a dynamic strain of 2.5% was applied at a temperature of ° C was measured. The lower the complex modulus (E '), the lower the loss tangent (tan)
The higher the δ), the better the grip performance. ta
The value of nδ / E ′ was expressed as an index, with the case of Comparative Example 1 taken as 100. The larger the index, the better the grip performance.

(Actual Vehicle Test) A tread was manufactured by bonding the manufactured sheets to a predetermined shape. Using this tread, a tire was manufactured by a conventional method. Automatic 2
The grip performance and abrasion performance were evaluated by mounting the vehicle on a wheel and traveling on a circuit of 4 km per lap. The larger the index, the higher the grip performance and wear performance.

Table 1 shows the results. Comparative Examples 1 to 4 are formulations of conventional general high-performance tires. With such a composition, it was not possible to satisfy both the grip performance and the wear resistance performance. Examples 1 to 3 had specific blending amounts and crosslinking point densities, all of which were excellent in both abrasion resistance and grip performance.

[0048]

[Table 1]

[0049]

According to the present invention, it is possible to provide a rubber composition which is excellent in both abrasion resistance and grip performance by specifying the content and the crosslinking point density.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Mine 3-6-9, Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo F-term in Sumitomo Rubber Industries, Ltd. (reference) 4J002 AC011 AC061 AC071 AC081 AE052 BB181 DA038 DJ016 EX037 EX057 EX077 EX087 FD016 FD018 FD022 FD140 FD150 FD207 GN01

Claims (2)

[Claims] 1. 100 parts by weight of a rubber component, silica 50-1
In a rubber composition containing 40 parts by weight, 30 to 70 parts by weight of an oil, and 3 to 20% by weight of a silane coupling agent with respect to silica, the weight of silica relative to 100 parts by weight of a rubber component is a part by weight And the crosslink point density ρ%
Is a rubber composition for a tire tread that satisfies the formula: ρ ≧ −0.5 × a + 270 (1). 2. The rubber composition further contains 5 to 70 parts by weight of carbon black based on 100 parts by weight of the rubber component, and the amount of each added is 5 to the total amount of silica and carbon black.
The rubber composition for a tire tread according to claim 1, which is 0 to 95% by weight and 5 to 50% by weight.