JPH0739510B2 - Tire tread rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention provides a vinyl aromatic / diene copolymer having a large hysteresis loss, excellent road surface gripping force, and good fracture strength and wear resistance. The present invention relates to a high performance sports tire tread rubber composition having excellent heat resistance. In the present invention, the high performance competition tires mean racing tires for two-wheeled vehicles and four-wheeled vehicles.

(Prior Art) Conventionally, butyl rubber, halogenated butyl rubber, emulsion-polymerized styrene / butadiene copolymer rubber having a high styrene content and the like have been used in order to improve the road surface gripping force in a tire tire for competition.

(Problems to be solved by the invention) However, the rubber material having a large hysteresis loss such as butyl rubber is higher than diene rubbers such as high cis polyisoprene rubber, natural rubber, high cis polybutadiene rubber and emulsion-polymerized styrene butadiene rubber. Co-vulcanizability and breaking strength with the diene rubber are poor. Emulsion-polymerized styrene-butadiene copolymer rubber having a high styrene content is not preferable because it often causes blowout under severe use conditions such as competition.

Therefore, the object of the present invention is to solve the above-mentioned problems, namely, the component rubber has excellent co-vulcanizability, a large hysteresis loss, excellent heat resistance, and good fracture strength and wear resistance. Another object of the present invention is to provide a high performance competitive tire tread rubber composition.

(Means for Solving the Problems) The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, a rubber composition containing a specific vinyl aromatic / diene copolymer is suitable for this purpose. It has been confirmed that the present invention has been achieved.

That is, the present invention, in a hydrocarbon solvent, a specific vinyl aromatic-diene copolymer obtained by a polymerization reaction using an organolithium compound as an initiator, or a mixture of 10% by weight or more thereof and a diene rubber. It is a high-performance sports tire tread rubber composition containing a rubber component, which solves the above problems.

The vinyl aromatic-diene copolymer used in the present invention is a copolymer of a monomer aromatic vinyl compound and a diene compound.

As the aromatic vinyl compound, styrene, p-methylstyrene, m-methylstyrene, p-tert-butylstyrene, α-methylstyrene, chloromethylstyrene,
Examples include vinyltoluene and the like. As a preferable example,
Examples thereof include styrene, p-methylstyrene and α-methylstyrene.

As the diene compound, butadiene, isoprene, pentadiene, 2,3-dimethylbutadiene and the like are used, and butadiene is preferable.

As the diene rubber used for blending in the present invention, various diene rubbers are used. Particularly, as the diene rubber having a glass transition temperature Tg of −60 ° C. or higher, an emulsion-polymerized styrene / butadiene copolymer having a high styrene content is used. Polymer rubber, acrylonitrile / butadiene copolymer rubber, chloroprene rubber, and the like are preferable, and emulsion-polymerized styrene / butadiene copolymer rubber having a high styrene content is particularly preferable.

In the present invention, when the vinyl aromatic / diene copolymer is less than 10% by weight of the rubber component, the improvement effect on abrasion resistance, heat resistance, grip property, etc. is small, so 10% by weight
The above content is required.

In the vinyl aromatic / diene copolymer, the percentage of vinyl bond units based on the entire diene polymerized portion is 40%.
If it is less than 40%, the heat resistance is poor, and if it is too large, the breaking strength is poor.

Further, in the vinyl aromatic-diene copolymer, when the content of the bound vinyl aromatic compound is small, the hysteresis loss is small, and the breaking strength is poor, and when the content is too large, the block chain of the bound vinyl aromatic compound is The elastic modulus in the operating temperature range (room temperature to 150 ° C.) increases and the temperature dependence is large, and the fracture strength is also poor. Therefore, the content of the bound vinyl aromatic compound is preferably 31 to 50% by weight, particularly preferably 31 to 40% by weight.

In the diene rubber used as a blend, it is preferable that the glass transition temperature Tg is −60 ° C. or higher in terms of wear resistance, heat resistance and grip property.

Although the Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the vinyl aromatic / diene copolymer of the present invention is not particularly limited,
From the viewpoint of workability, it is preferably 30 to 80.

In order to obtain a high hysteresis loss, it is specified that the rubber composition contains 50 to 200 parts by weight of the extender oil based on 100 parts by weight of the rubber component excluding the oil in the rubber component. If it exceeds 200 parts by weight, the breaking strength and abrasion resistance are poor, and a compounding amount in the range of 60 to 170 parts by weight is particularly preferable.

An aromatic oil is used as the extender oil, and those having a viscosity specific gravity constant of 0.900 to 1.100 shown in ASTM02501 are preferable, and those having 0.920 to 0.990 are particularly preferable.

As other compounding agents, commonly used compounding agents such as carbon black, filler, vulcanization accelerator, vulcanizing agent and the like can be used.

The butadiene-based copolymer of the present invention can be obtained by various production methods. To exemplify the industrial method, an organolithium compound initiator in a hydrocarbon solvent in the presence of an ether or a tertiary amine is used in a tank or column reactor to produce a small amount of 1,
This is a method of obtaining a copolymer by copolymerizing 1,3-butadiene containing 2-butadiene and a vinyl aromatic compound. In this case, if necessary, silicon halide, adipic acid diester, alkylene carbonate, divinylbenzene or the like is added in an appropriate amount at the final stage of the copolymerization reaction to perform a coupling reaction to modify the copolymer, or a catalyst. Various changes such as addition of either or both of the monomers are possible.

In the present invention, the glass transition temperature and Tg are DSC.
The temperature at which the curve of the plotted heat capacity changes with respect to the temperature measured by (differential scanning calorimeter) is defined as the glass transition temperature.

(Examples) Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

The polymers used in Examples and Comparative Examples were obtained by the following method, and the analysis results are shown in Table 1.

Sample A To a reactor having an internal volume of 20 equipped with a stirrer and a jacket, 20 g / min of butadiene containing 100 ppm of 1,2-butadiene as a monomer, 10 g / min of styrene, 150 g / min of cyclohexane as a solvent, and tetrahydrofuran. 1.5g / min, 0.032g of n-butyllithium as a catalyst for 100 monomers
Was continuously pumped in and the reactor temperature was controlled at 70 ° C. Silicon tetrachloride was continuously added at a ratio of 1/4 mol to n-butyllithium at the reactor top outlet,
This was introduced into a second reactor connected to the upper part of the reactor to carry out a coupling reaction. At the outlet of the second reactor, di-tert-butyl-p-cresol was added to 100 parts by weight of rubber.
0.5 parts by weight and then 37.5 parts by weight of aroma oil were added, and desolvation and drying were carried out by a conventional method.

Samples B, E and F A polymer was obtained by the same method as Sample A except that the charged composition of the monomers was changed.

Sample C A polymer was obtained by the same method as in Sample A except that 0.020 g of n-butyllithium was used per 100 g of the monomer and no coupling reaction was carried out.

Sample D With the same formulation as in Sample A, the polymerization reaction was carried out in the first reactor and the coupling reaction was not carried out in the second reactor, and 15 g / min of butadiene and 7 g / styrene of styrene were used as monomers.
min, n-butyllithium was continuously supplied to carry out a polymerization reaction at 70 ° C. At the outlet of the second reactor, 0.5 part by weight of di-tert-butyl-p-cresol was added to 100 parts by weight of rubber, and then 37.5 parts by weight of aromatic oil were added, and desolvation and drying were carried out by a conventional method.

Sample G, H A polymer was obtained in the same manner as Sample A except that the amount of tetrahydrofuran used was changed.

Examples 1 to 7 and Comparative Examples 1 to 6 A rubber compound was obtained from each sample shown in the above and Table 1 according to the compounding recipe of Table 2. Table 3 shows the tensile strength, blowout temperature, lap time in the cart test, and abrasion resistance of the vulcanizates obtained by vulcanizing these compounds under vulcanization conditions of 145 ° C. for 30 minutes.

As can be seen from Examples 1 to 7, the rubber composition is preferably used as a tread rubber composition for high performance sports tires used under severe conditions of use because of its excellent heat resistance, abrasion resistance and road surface gripping property. It

In contrast, the comparative example has a low blowout temperature and heat resistance,
Inferior in wear resistance and road surface grip.

(Effects of the Invention) As shown in the above Examples and Comparative Examples, the present invention was polymerized by an organolithium initiator as a treaded rubber composition for high performance sports tires used under severe usage conditions. By blending a specific vinyl aromatic / diene copolymer alone or in a specific ratio with a diene rubber, heat resistance / abrasion resistance and road surface gripping property are simultaneously satisfied.

This is something that cannot be achieved with conventional materials.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshihisa Fujinaga 2-11-24 Tsukiji, Chuo-ku, Tokyo Within Nippon Synthetic Rubber Co., Ltd. (72) Inventor Noboru Oshima 2-11-24 Tsukiji, Chuo-ku, Tokyo Within Japan Synthetic Rubber Co., Ltd. (56) Reference JP-A-56-163908 (JP, A) JP-A-58-36705 (JP, A) JP-A-56-112947 (JP, A) JP-A-59- 124943 (JP, A) JP-A-57-100146 (JP, A)

Claims (2)

[Claims] 1. A vinyl aromatic / diene copolymer obtained by a polymerization reaction using an organic lithium compound as an initiator in a hydrocarbon solvent, wherein a bound vinyl aromatic compound within a range of 31 to 50% by weight is used. A rubber component containing a copolymer of vinyl aromatic compound and butadiene alone or containing 10% by weight or more of the copolymer of vinyl aromatic compound and butadiene, containing 40 to 59% of vinyl-bonded butadiene units. A high performance sports tire red rubber composition, characterized in that the extension oil is blended in an amount of 50 to 200 parts by weight with respect to 100 parts by weight. 2. The tire tread rubber composition according to claim 1, wherein the diene rubber is an emulsion-polymerized styrene / butadiene copolymer rubber having a high styrene content and a glass transition temperature Tg of -60 ° C. or higher. .