JP2001214004A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for tire tread having much more simultaneously improved both characteristics of rolling resistance and wet gripping performance than those of conventional levels. SOLUTION: This rubber composition for tire treated is characterized in that 100 pts.wt. of a rubber component containing >=50 wt.% of a styrene- butadiene copolymer rubber is compounded with 10-80 pts.wt. of silica and the styrene-butadiene copolymer rubber is composed of (A) >=30 wt.% of a solution polymerization styrene-butadiene copolymer rubber containing a molecular chain terminal modified with an amino group, (B) >=30 wt.% of a high vinyl styrene-butadiene rubber copolymer rubber having >=50 wt.% vinyl content and (C) the rest of another styrene-butadiene copolymer rubber.

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 which has simultaneously improved low rolling resistance and wet grip.

[0002]

2. Description of the Related Art In recent years, with the emphasis on resource saving, the demand for lower fuel consumption of automobiles has become more and more strict. In the tire industry as well, it is required that the rolling resistance be reduced to contribute to lower fuel consumption. Have been. In order to reduce the rolling resistance of the tire, it is preferable to use a rubber material having high rebound resilience when vulcanized rubber is used. However, such a material tends to decrease wet grip performance.

[0003] In order to achieve both rolling resistance and wet gripping properties, a solution-polymerized styrene-butadiene copolymer rubber is used as a rubber material, and the styrene content, vinyl content or three-dimensional structure of the vulcanized rubber is adjusted. Loss tangent at the temperature of 0 ° C. (t
an δ) is increased while the value of the loss tangent (tan δ) at a temperature of 50 ° C. is reduced to balance the two characteristics. However, adjustment of these microstructures alone has limitations in improving the overall level of both properties.

[0004]

SUMMARY OF THE INVENTION According to the present invention, by mixing three kinds of styrene-butadiene copolymer rubbers having different microstructures, both the rolling resistance and the wet grip property are simultaneously improved as compared with the conventional level. It is an object of the present invention to provide a further improved rubber composition for a tire tread.

[0005]

According to the present invention, there is provided a rubber component 100 containing at least 50% by weight of a styrene-butadiene copolymer rubber.
10 to 80 parts by weight of silica is blended with respect to parts by weight, and the styrene-butadiene copolymer rubber comprises: (A) 30% by weight or more of a solution-polymerized styrene-butadiene copolymer rubber having a molecular chain terminal modified with an amino group. (B) a tire tread characterized by comprising a high vinyl styrene-butadiene copolymer rubber having a vinyl content of 50% by weight or more and 30% by weight or more, and (C) a remainder comprising another styrene-butadiene copolymer rubber. It is a rubber composition for use.

In another invention, 10 to 80 parts by weight of silica is mixed with 100 parts by weight of a rubber component containing 50% by weight or more of styrene-butadiene copolymer rubber, and the styrene-butadiene copolymer rubber comprises: (A) 30% by weight or more of a solution-polymerized styrene-butadiene copolymer rubber having one or both ends of a molecular chain modified with a functional group having strong interaction with carbon or silica; and (B) a high vinyl having a vinyl content of 50% by weight or more. A rubber composition for a tire tread, comprising 30% by weight or more of a styrene-butadiene copolymer rubber and (C) the rest of the styrene-butadiene copolymer rubber.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Of the styrene-butadiene copolymer rubber used in the rubber composition of the present invention, at least 30% by weight of a solution-polymerized styrene-butadiene copolymer in which one or both ends of a molecular chain are modified with amino groups. Polymerized rubber (hereinafter referred to as terminal-modified SBR).

Here, the terminal-modified SBR is produced by a conventional solution polymerization, and an amino compound is further added thereto and reacted in the presence of an alkali metal catalyst, for example, n-butyllithium, so that the terminal of the SBR has the following formula ( The functional group of 1) is introduced.

[0009]

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In the formula, X represents an oxygen atom or a sulfur atom. The method of modifying the terminal of SBR can be, for example, the method disclosed in JP-A-63-150338. Amino compounds added for terminal modification include N, N-dimethylformamide, N, N-diethylformamide, N, N-diethylacetamide,
Aminoacetamide, N-phenyldiacetamide,
N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, propionamide, N, N-dimethylpropionamide, 4-pyridylamide, N, N-dimethyl-4-pyridylamide, N, N-dimethylbenzamide, p -Aminobenzamide, N-acetyl-N-
2-naphthylbenzamide, nicotinamide, N, N-
Diethylnicotinamide, succinamide, maleic amide, N, N, N ', N'-tetramethylmaleamide, 1,2-cyclohexanecarboxamide, N-
Methyl-1,2-cyclohexanedicarboximide, oxamide, N, N-dimethyl-2-furamide, N, N-
Dimethyl-N ', N'-(2-dimethylamino) vinylamide, N '-(2-methylamino) vinylamide, urea, N, N'-dimethylurea, methyl carbamate,
Methyl N, N-diethylcarbamate, ε-caprolactam, N-methyl-ε-caprolactam, N-acetyl-ε-caprolactam, 2-pyrrolidone, N-methyl-
2-pyrrolidone, N-acetyl-2-pyrrolidone, 2-
There are piperidone, 2-quinoline, N-methyl-2-quinoline, 2-indolinone, isocyanuric acid, and the like. Further, a sulfur-containing compound in which an oxygen atom of these compounds is replaced with sulfur can be used. The ratio of terminal modification is 10 to 10
A range of 0% is preferred.

The present invention also relates to a styrene-butadiene copolymer rubber modified with an amino group and a carbon such as a tin compound, a silicon compound, an isocyanate or 4,4'-bis (diethylamino) benzophenone, or silica. A solution-polymerized styrene-butadiene copolymer rubber modified with a strong functional group can also be blended. The styrene-butadiene copolymer rubber can contain two or more kinds of the functional groups to be modified, and the terminal modification ratio is in the range of 10 to 100%.

For modification with the above functional group, for example, tin tetrachloride is added to a styrene-butadiene copolymer having terminal lithium ions obtained by solution-polymerizing styrene and butadiene with an n-butyllithium catalyst, so that the terminal is terminated. Modified with tin.

The terminal is modified with silicon by adding silicon tetrachloride to the copolymer solution.

Further, when an isocyanate compound is added to the solution of the copolymer, an isocyanate group is introduced into the molecular chain as shown in the formula (2), and 4,4'-bis-
By adding (diethylamino) -benzophenone, the compound is added to the molecular terminal as shown in formula (3). In the formulas (2) and (3), m represents an integer, and R and R 'each represent an alkyl group.

[0015]

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[0016]

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In the molecule of the terminal-modified SBR, the styrene content is 15 to 40% by weight, more preferably 15 to 25%.
% And the vinyl content is adjusted in the range from 40 to 70% by weight. By adjusting the structure of the terminal modification, the vinyl content and the styrene content within the above ranges, the reinforcing effect by silica is improved, the basic properties such as tensile strength and elongation are improved, and the loss tangent at a temperature around 50 ° C. is further improved. (Tan δ)
Has the effect of decreasing the value of and increasing the low rolling resistance.

The above effect can be expected when the amount of the terminal-modified SBR is 30% by weight or more of the whole styrene-butadiene copolymer rubber, and is preferably in the range of 30 to 60% by weight.

Next, in the present invention, the vinyl content is 50% by weight.
The above-mentioned high vinyl styrene-butadiene copolymer rubber (hereinafter referred to as high vinyl SBR) is contained in an amount of 30% by weight or more of the whole styrene-butadiene copolymer rubber. Here, the high vinyl SBR mainly contributes to an increase in the loss tangent (tan δ) of the vulcanized rubber at a temperature of 0 ° C., and enhances wet grip properties. Therefore, such an effect cannot be expected at less than 30% by weight. High vinyl SB
The vinyl content of R preferably ranges from 60 to 75% by weight.

In the present invention, styrene-butadiene copolymer rubbers other than those described above, for example, emulsion-polymerized styrene-butadiene copolymer rubber, solution-polymerized styrene-butadiene copolymer rubber (styrene content of 5 to 40% by weight, vinyl content of 10
-50% by weight), high trans styrene-butadiene copolymer rubber (trans content 70-95%), high vinyl SBR
-Low vinyl SBR block copolymer rubber and the like are mixed.

In the present invention, in addition to the styrene-butadiene copolymer rubber, other rubber components, especially diene rubbers such as natural rubber, polyisoprene rubber, low cis polybutadiene rubber, high cis polybutadiene rubber,
Styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene of solution polymerization and emulsion polymerization
Butadiene-isoprene copolymer rubber, emulsion-polymerized styrene-acrylonitrile-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, etc. are used according to the required characteristics, but preferably have good compatibility with the styrene-butadiene copolymer rubber. By using no rubber component, the characteristics of each rubber can be utilized, and as a result, the value of loss tangent (tan δ) at a temperature of 0 ° C. can be increased, and the wet grip property of the rubber composition can be further improved. it can. These other rubber components are 50% by weight or less, preferably 20 to 50% by weight of the entire rubber component.
Range.

As the silica used in the present invention, those generally used in tread rubber compositions for tires can be used. For example, dry-process white carbon, wet-process white carbon, colloidal silica, precipitated silica, and the like are exemplified, and wet-process white carbon mainly containing hydrous silicate is preferred.

Nitrogen adsorption specific surface area of silica (BET method)
And usually 80 to 350 m ² / g, preferably 100 to ²
It is in the range of 50 m ² / g. If the specific surface area of the silica is smaller than the above range, the reinforcing property is inferior, and if it is large, the workability is inferior, and the abrasion resistance and the rebound resilience become insufficient. Here, the nitrogen adsorption specific surface area is measured by the BET method according to ASTM D3037-81.

Silica is used in an amount of 10 to 80 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the rubber component. When the amount is less than 10 parts by weight, the reinforcing property is inferior, and conversely 8
If the amount exceeds 0 parts by weight, the viscosity of the unvulcanized rubber composition increases, resulting in poor processability.

The addition of a silane coupling agent to the rubber composition of the present invention has an effect of further improving rolling resistance and abrasion resistance. The silane coupling agent is
For example, N- (β-aminoethyl) -γ-aminopropyltriethoxysilane, N- (β-aminoethyl)-
γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-trimethoxysilylpropyl Tetrasulfides such as benzothiazyltetrasulfide, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxy-ethoxy) silane, β-
(3,4-epoxycyclohexyl) -ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane and the like can be used. .

The mixing ratio of the silane coupling agent is 1 to 30 parts by weight, preferably 3 to 30 parts by weight, per 100 parts by weight of silica.
The range is 10 parts by weight. If the compounding ratio is less than 1 part by weight, no improvement in the affinity between the rubber component and silica can be expected, and if it exceeds 30 parts by weight, the effect of the silane coupling agent compounding is saturated, which is not economical.

The rubber composition of the present invention can be kneaded with components according to a conventional method. In addition to the above compounding agents, vulcanizing agents such as sulfur and peroxide, vulcanization accelerators such as thiazole, thiuram, sulfenamide and guanidine, vulcanization accelerators such as stearic acid and zinc white are used in accordance with ordinary methods. An agent, an activator such as diethyl glycol or polyethylene glycol, a reinforcing agent such as calcium carbonate, a plasticizer, an antioxidant, and the like can be appropriately compounded according to the purpose.

In the present invention, the nitrogen adsorption specific surface area (BE)
T method) is 70 to 170 m ² / g and the DBP oil absorption is 70
１４０140 ml / 100 g of carbon black is added in an amount of 5 to 80 parts by weight, preferably 1 to 100 parts by weight of the rubber component.
It is desirable to add 0 to 40 parts by weight. The total amount of silica and carbon black is 100% of the rubber component.
40 to 100 parts by weight based on parts by weight.

In order to knead the components, first, the rubber component and silica or carbon black are mixed using a mixer such as a roll or a Banbury, and then the other components are added and mixed, whereby the dispersibility is improved. Thus, a uniform rubber composition can be obtained.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Examples 1 to 3 and Comparative Examples 1 to 6 Rubber compositions were prepared by changing the types of rubber components using the basic formulations shown in Table 1. Vulcanization of rubber composition is 165 ° C
For 10 minutes.

The detailed specifications of the various styrene-butadiene copolymer rubbers (SBR) used in Table 3 are shown in Table 2. The specifications of the various compounding agents shown in Table 1 are as follows.

[0033]

[Table 1]

Note 1) Carbon: Seast KH (manufactured by Tokai Carbon Co., Ltd.) Note 2) Silica: Ultrasil VN3 (manufactured by Degussa) Note 3) Silane coupling agent: Si69 (manufactured by Degussa) Note 4) Sun protection 6C : Ozonone 6C (Seiko Chemical Co., Ltd.) * 5) Accelerator CZ: Noxeller CZ (Ouchi Shinko Chemical Co., Ltd.) * 6) Accelerator D: Noxeller D (Ouchi Shinko Chemical Co., Ltd.) Evaluation of rubber composition The method is as follows.

(1) Tensile properties Measured in accordance with JIS K6251.

(2) Hardness (Shore Hardness) Measured according to JIS K6253.

(3) Wet grip property The viscoelasticity of the rubber was measured and evaluated by the value of tan δ at 0 ° C. The index was indicated as an index with Comparative Example 1 as 100. The higher the number, the better.

Measurement conditions: initial strain 10%, frequency 10 Hz, dynamic strain ± 1% (4) Rolling resistance The rubber was measured for viscoelasticity and evaluated by the value of tan δ at 50 ° C. The measurement conditions are as described above. The index was indicated as an index with Comparative Example 1 as 100. The lower the number, the better.

[0039]

[Table 2]

[0040]

[Table 3]

The evaluation results are shown in Table 3 and in the graph of FIG. The example of the present invention is shifted to the right side of the graph as compared with the comparative example, and it is recognized that both the rolling resistance and the wet grip property are improved in a well-balanced manner.

The embodiments and examples disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0043]

As described above, the present invention provides three kinds of styrene-
Since the butadiene copolymer rubber is mainly composed of a rubber component and is composed of a rubber composition in which silica is blended, a rubber composition for a tire tread having improved rolling resistance and wet grip properties can be obtained at the same time.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between rolling resistance and wet grip.

Claims (2)

[Claims] 1. A styrene-butadiene copolymer rubber is mixed with 50
10 to 80 parts by weight of silica is blended with respect to 100 parts by weight of a rubber component containing not less than 10% by weight, and the styrene-butadiene copolymer rubber comprises: (A) a solution in which one or both ends of a molecular chain are modified with amino groups. 30 styrene-butadiene copolymer rubber
(B) 30% by weight or more of a high vinyl styrene-butadiene copolymer rubber having a vinyl content of 50% by weight or more, and (C) the remainder composed of another styrene-butadiene copolymer rubber. Rubber composition for tire treads. 2. A styrene-butadiene copolymer rubber is mixed with 50
10 to 80 parts by weight of silica is blended with respect to 100 parts by weight of the rubber component containing not less than 10% by weight, and the styrene-butadiene copolymer rubber has the following properties: (A) one end or both ends of the molecular chain interacts with carbon or silica; (B) a high-vinylstyrene-butadiene copolymer rubber having a vinyl content of 50% by weight or more; and 30% by weight or more of a solution-polymerized styrene-butadiene copolymer rubber modified with a strong functional group. A rubber composition for a tire tread, wherein the remainder is composed of another styrene-butadiene copolymer rubber.