JPH0481437A - Improved rubber composition - Google Patents

Abstract

PURPOSE:To provide the subject rubber composition containing two kinds of specified styrene-butadiene copolymers and a rubber-like polymer in a specified ratio, excellent in abrasion resistance, impact resilience, tensile strength, wet skid resistance, etc., and useful as a tire, a belt, a hose, etc. CONSTITUTION:A rubber composition containing (A) a styrene-butadiene copolymer obtained by using a polar organic compound in the presence of an organic alkali metal catalyst in an inert solvent and having 5-60wt.% styrene content, 35-60% vinyl bond content and <42% 1,4-trans bond content in butadiene part and 55000-350000 weight-average molecular weight, (B) another styrene-butadiene copolymer having 5-40wt.% styrene content, 1-25% vinyl bond content in butadiene part and <=5wt.% block styrene content and (C) one or more rubber-like polymers selected from natural rubber, polyisoprene and a polybutadiene having 1-20% vinyl bond content as the raw materials in (20-80):(80-20) weight ratio of (A):(B), 10-40wt.% styrene content in (A+B), 30-53% vinyl bond content in butadiene part and >=25 pts.wt. (A+B) and <75 pts.wt. (C) component.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention relates to a rubber composition containing two or more types of styrene-butadiene copolymer rubbers having different structures, and more particularly, to a rubber composition containing two or more types of styrene-butadiene copolymer rubbers having different amounts of vinyl bonds in the butadiene moiety. [0002] Relating to a rubber composition containing a polymer rubber as a rubber component, having good processing properties and an improved balance between abrasion resistance and wet skid resistance (slip resistance in wet rolling)

[Conventional technology]

Raw material rubber used in various vulcanized rubber products including automobile tires, anti-vibration rubber, footwear, etc.
Natural rubber, polyisoprene rubber, emulsion polymerized styrene-butadiene copolymer rubber, high cis-polybutadiene rubber,
Low cis-polybutadiene rubber, solution polymerized styrene-butadiene copolymer rubber, etc. are used alone or in combination.
It is used as a raw material rubber for various vulcanized rubber products by blending more than one species. [0003] Among the various raw material rubbers, polybutadiene rubber or styrene-butadiene copolymer rubber obtained using a lithium-based catalyst is a polymer that has been attracting attention in recent years because of the relatively wide range of variability of its polymer structure. For example, in Japanese Patent Publication No. 49-4311, microstructures of 1 and 2
-Bound amount (synonymous with vinyl bond) is 25-50%, 1.4
- A tire rubber composition using polybutadiene having a trans bond content of 15 to 55% and a 1,4-cis bond content of 10 to 40% is disclosed. When polybutadiene having such a microstructure is used in tire treads, it exhibits satisfactory abrasion resistance and wet skid resistance to some extent, but on the other hand, processability is not necessarily satisfactory, and the tensile strength of the vulcanizate is is also not enough. [0004]

[Problem to be solved by the invention]

On the other hand, when a styrene-butadiene copolymer obtained by solution polymerization with a lithium catalyst and having a vinyl bond content of 15% or less is used for a tire tread, the wear resistance is lower than that of emulsion polymerized styrene-butadiene. Although the performance is better than when using a polymer, the wet skid resistance is inferior, and when a solution-polymerized styrene-butadiene copolymer with a vinyl bond content of about 20 to 30% is used, the vulcanizate There was a problem with wear resistance. [0005] Furthermore, in recent years in the rubber industry, in order to improve productivity, vulcanization has been performed at higher temperatures and for shorter times than conventional rubber vulcanization conditions. In such cases, there will be a difference in the vulcanization state between the center and the outside of the molded product due to thermal conductivity, resulting in what is called ``uncured''.
This phenomenon is likely to occur, causing deterioration of the physical properties of the vulcanizate. In particular, natural rubber, polyisoprene rubber, low cis-polybutadiene rubber, high cis-polybutadiene rubber, styrene rubber with a vinyl bond content of 15% or less
Butadiene copolymer rubber and the like are rubbers that are susceptible to reversion from vulcanization, and there has been a demand for a raw material rubber that can be cured at high temperatures and in short periods of time, which can overcome this drawback. [0006]

[Means to solve the problem]

As a result of intensive studies to improve the drawbacks of the various raw material rubbers mentioned above, the present inventors have developed a styrene-butadiene copolymer with a relatively small amount of vinyl bonds and a styrene-butadiene copolymer with a relatively large amount of vinyl bonds. A rubber composition containing one or more rubbery polymers selected from natural rubber, polyisoprene rubber, and polybutadiene rubber with a vinyl bond content of 1 to 20%. The vulcanizate has excellent properties, has little reversion during vulcanization, has sufficient tensile strength, and has an improved balance between wet skid resistance and abrasion resistance, making it suitable for use in automobile tires, industrial products, and anti-vibration rubber. The present invention has been achieved by discovering that it is suitable for various rubber uses such as rubber. [0007] The present invention comprises (A) component: a styrene-butadiene copolymer having a styrene content of 5 to 60% by weight and a vinyl bond amount of the butadiene moiety of 35 to 80%; (B) component a distyrene content of 35 to 80%; 5
~40% by weight, the amount of vinyl bonds in the butadiene moiety is 1-2
5% styrene-butadiene copolymer (C) component:
Natural rubber, polyisoprene, vinyl bond content 1-20%
This is a rubber composition using as a raw material rubber any one or more rubber-like polymers of polybutadiene, consisting of component (A) and component (B).
The weight ratio of the components is 20-80:80-20, and (A)
A rubber composition in which the total amount of component (B) and component (B) is 25 parts by weight or more and component (C) is 75 parts by weight or less. [0008] The present invention will be described in detail below. The styrene-butadiene copolymer used as component (A) of the rubber composition of the present invention has a styrene content of 5 to 60% by weight, preferably 10 to 50% by weight. If the styrene content is less than 5% by weight, processability will be insufficient, and the resulting rubber composition will have poor tensile strength and wet skid resistance. On the other hand, if the amount exceeds 60% by weight, the resulting composition will have poor anti-friction elasticity and abrasion resistance. [0009] Amount of vinyl bonds (amount of 1,2-bonds) in the microstructure of the butadiene moiety of the styrene-butadiene copolymer of component (A)
is 35% or more and less than 60%, preferably 40% or more and less than 60%
The range is less than or equal to If the amount of vinyl bonds is less than 35%, the effect of inhibiting the recursion of the composition during vulcanization will not be sufficient, and the resulting composition will have poor wet skid resistance. The wear resistance is poor and it is not practical. [00,10] (A) A polymer in which the styrene in the styrene-butadiene copolymer is uniformly present along the molecular chain, or a polymer in which the amount of styrene increases or decreases along the molecular chain. A block copolymer having one or more blocks consisting of a copolymer or polystyrene with a high amount of styrene and one or more blocks consisting of a copolymer or polybutadiene with a low amount of styrene. The amount of block styrene in the copolymer (J, Polym, Sci
, 1 429 (1946)) is preferably 5% by weight or less of the copolymer from the viewpoint of heat generation of the composition. [0011] Also, a copolymer in which the vinyl bonds in the butadiene moiety are uniformly present along the molecular chain like the above-mentioned styrene, a copolymer in which the amount of vinyl bonds increases or decreases along the molecular chain,
Any copolymer in which a portion with a large amount of vinyl bonds and a portion with a small amount of vinyl bonds exist in the form of a block, or a copolymer in which these are combined can be used as the component (A) of the present invention. [0012] The weight average molecular weight of the styrene-butadiene copolymer of component (A) is 55,000 or more and less than 350,000, preferably 82,500 or more and less than 350,000, and the molecular weight distribution (weight average molecular weight and the number average molecular weight (Mw/Mn) is preferably 1.1 to 4.0, more preferably 1.2 to 3.0.The above range depends on the physical properties and processability of the copolymer. This is a preferable range for retention. [0013] Component (A) is present in an amount of 20 to 80 parts by weight, preferably 25 to 75 parts by weight, relative to 100 parts by weight of the total amount of component (A) and component (B) (described later). When used in parts by weight and outside the above composition range, the improvement effect is slight compared to when each is used alone.Next, the styrene-butadiene copolymer used as component (B) of the present invention is: The copolymer has a styrene content of 5 to 40% by weight, preferably 5 to 30% by weight. If the styrene content is less than 5% by weight, the processability is poor and the wet skid resistance of the resulting composition is poor. not enough,
On the other hand, if the styrene content exceeds 40% by weight, it will adversely affect the wear resistance of the resulting composition. [0014] The amount of vinyl bonds in the microstructure of the butadiene moiety of the styrene-butadiene copolymer of component (B) is 1% or more and less than 25%. If the amount of vinyl bonds exceeds 25% by weight, the resulting composition will have insufficient wear resistance. Regarding the styrene-butadiene copolymer of component (B), the styrene in the copolymer may exist uniformly along the molecular chain, or the amount of styrene may increase or decrease along the molecular chain. one or more blocks consisting of a styrene-enriched copolymer or polystyrene;
Any copolymer with a small amount of styrene or a copolymer with one or more blocks made of polybutadiene may be used, but the amount of block styrene in the copolymer must be 5% by weight or less of the copolymer. It is. When the amount of block styrene exceeds 5% by weight of the copolymer, the abrasion resistance of the resulting composition deteriorates, and other properties such as impact resilience and heat generation properties also deteriorate. [0015] The number average molecular weight of the styrene-butadiene copolymer of component (B) is preferably in the range of 50,000 to 400,000, more preferably 75,000 to 300,000, and the molecular weight distribution (Mw/Mn) is preferably 1.1 to 4
．． 0, more preferably 1.2 to 3.0. The above range is a preferable range in terms of maintaining the physical properties and processability of the copolymer. [0016] Component (B) is the total amount of component (A) and component (B) 100
20 to 80 parts by weight, preferably 25 to 80 parts by weight
It is used in a composition of 75 parts by weight. In the present invention, component (A) and component (B) are used within the above composition range, but the styrene content as a mixed composition of component (A) and component (B) is 10 to 40% by weight.
The processability and abrasion resistance of the resulting composition can be improved by using the structures and compositions of components (A) and (B) such that the amount of vinyl bonds in the butadiene moiety is 30% or more and less than 53%. The styrene content is preferably 15 to 35% by weight, and the vinyl bond amount is 35 to 42%, which is necessary in terms of balance with the physical properties. [0017] The styrene-butadiene copolymer of the component (A) and the styrene-butadiene copolymer of the component (B) may be obtained by any manufacturing method and meet the above-mentioned limiting conditions. For example, it can be used as a raw rubber component of the composition of the present invention. The styrene-butadiene copolymer of component (A) is a copolymer with a higher vinyl bond content than the styrene-butadiene copolymer generally used for rubber applications, and these (
The copolymer used as component A) is produced by using n-butyllithium, 5eC as a polymerization catalyst in an inert solvent such as hexane, cyclohexane, or benzene.
- Using organic lithium such as butyl lithium or other organic alkali metal compound, and if necessary, as a co-catalyst component, alkoxide such as potassium butoxide, organic acid salt such as dodecylbenzenesulfone hydrochloric acid, sodium stearate, etc. are typical examples. A method of copolymerizing styrene and butadiene using an organic compound as described above and a polar organic compound such as ether, polyether, tertiary amine, polyamine, thioether, hexamethylphosphortriamide, etc. as a compound for adjusting the vinyl bond amount. obtained by. The amount of vinyl bonds can be controlled by the amount of the polar compound added and the polymerization temperature. [0018] Furthermore, coupling the polymer chain having an active end obtained by the above method with a polyfunctional compound such as silicon tetrachloride, tin tetrachloride, or a polyepoxy compound;
By adding a branching agent such as divinylbenzene to the polymerization system, a branched or radial copolymer can be obtained. In addition, in the above polymerization method, by adjusting the method of adding monomers, changing the compound that adjusts the amount of vinyl bonds, and changing various polymer conditions such as changing the polymerization temperature in the middle of the polymerization reaction, it is possible to change the molecular chain. Among them, the styrene content and the amount of vinyl bonds can be continuously increased or decreased, or the polymer can be in the form of blocks. [0019] Furthermore, acetylene, 1,2-butadiene, fluorene,
Various molecular weight regulators such as toluene, primary amines, secondary amines, etc. can also be used. Next, the styrene-butadiene copolymer used as component (B) is a copolymer having a smaller amount of vinyl bonds than the styrene-butadiene copolymer used as component (A). A typical manufacturing method for these copolymers used as component (B) is the same as the method for obtaining the styrene-butadiene copolymer as component (A), except that the amount of vinyl bonds is set to a predetermined amount. Therefore, a method is used in which the amount of polar organic compound added is reduced or polymerization is performed without using it. In addition, when copolymerizing styrene and butadiene without using a polar organic compound, the difference in reaction rate between the two tends to result in a copolymer with block styrene, so a copolymer with a small amount of block styrene is used. In order to obtain this, it is desirable to adjust the method of adding monomers or to add a compound such as dodecylbenzenesulfonate that does not significantly increase the amount of vinyl bonds. [0020] It is also possible to obtain the styrene-butadiene copolymer used as component (B) of the present invention by a polymerization method other than polymerization using a lithium catalyst, such as a method using emulsion polymerization. The polymerization process for obtaining component (A) and component (B) can be a batch polymerization process, a continuous polymerization process, or a combination thereof. [0021] The rubbery polymer of component (C) used in the present invention is natural rubber, polyisoprene rubber, and has a vinyl bond content of 1 to 20%.
One or more rubbery polymers selected from polybutadiene rubber. These rubber-like polymers are raw material rubbers that are generally used in many rubber applications. Polyisoprene rubber is a polymer obtained by polymerizing isoprene with a Ziegler-based catalyst or a lithium-based catalyst. The amount is 1~
The 20% polybutadiene rubber is typically a high cis polybutadiene rubber obtained using a Ziegler catalyst or a low cis polybutadiene rubber obtained using a lithium catalyst [0022] Rubber of the Invention In the composition, the rubber-like substance of the component (C), the components (A) and the components (B) are contained in a total amount of 25 parts by weight or more of the components (A) and (B), and 75 parts by weight of the component (C). Hereinafter, it is preferably used in a composition in which the total amount of component (A) and component (B) is 30 parts by weight or more and component (C) is 70 parts by weight or less. If the sum of component (A) and component (B) is less than 25 parts by weight,
The effect of improving the recovery of vulcanization of component (C) in the vulcanization process of the composition is remarkable. [0023] Next, the characteristics of the rubber composition obtained by the present invention will be described below. The characteristics of a rubber composition in which component (C) is added to components (A) and (B) are as follows: (1) Natural rubber or polyisoprene rubber used as component (C) has a vinyl bond content of 1 to 2;
It has the effect of improving vulcanization recovery of 0% polybutadiene rubber. (2) Compared to the case where only one or two of the components (A), (B), and (C) are used as raw rubber, the wear resistance, impact resilience, tensile strength, wet skid resistance, etc. It has a good balance of properties and has excellent workability. [0024] As shown above, the rubber composition according to the present invention is a useful rubber composition that could not be achieved by using conventional raw material rubber or a combination of conventional raw material rubbers, and is useful for automobile tires, anti-vibration rubber. It is suitable for various uses such as , industrial supplies, and footwear. The rubber composition of the present invention comprises the above-mentioned component (A), component (B), (
Component C) is a raw material rubber, and by adding various compounding agents to it and molding and vulcanizing it, it can be used for various uses including tires. [0025] The compounding agents added to the rubber composition include reinforcing agents,
There are softeners, fillers, vulcanizing agents, vulcanization accelerators, vulcanization aids, colorants, flame retardants, lubricants, blowing agents, and other compounding agents, and these may be added as appropriate depending on the use of the composition. selected and used. Carbon black is a typical reinforcing agent, and various types of reinforcing agents with different particle sizes or stractures obtained by various manufacturing methods are used.
Carbon blacks such as 15AF, HAF, and FEF are suitably used for applications centered on tires. The amount of carbon black to be added is 10 to 150 parts by weight, preferably 40 to 100 parts by weight, based on 100 parts by weight of the raw material rubber used for the force plate, taking into account the amount of process oil to be added if necessary. section is used. The type and amount of carbon black added are appropriately adjusted depending on the intended use of the rubber composition, and two or more types may be used in combination. [0026] Other reinforcing agents include inorganic reinforcing agents such as silica and activated calcium carbonate, high styrene resin, and phenol.
Formaldehyde resin etc. are used, and these inorganic or organic reinforcing agents are used in an amount of 1 to 1 to 100 parts by weight of raw rubber.
100 parts by weight, preferably 5 to 50 parts by weight are used. Typical softeners added as needed include process oils, including paraffinic, naphthenic,
Various aromatic rubbers are suitably used in the rubber composition, and are used in an amount of 2 to 100 parts by weight, preferably 5 to 70 parts by weight, per 100 parts by weight of raw rubber. It is also possible to use an oil-extended polymer in which the process oil is added to the raw rubber in advance. Other softeners include liquid paraffin, coal tar, fatty oils, and sub. [0027] Sulfur is a typical vulcanizing agent, and raw rubber 1
01 to 10 parts by weight, preferably 0.00 parts by weight.
2 to 5 parts by weight are used. Other vulcanizing agents include sulfur compounds such as sulfur chloride, morpholine disulfide, and alkylphenol disulfide, and peroxides, which may be used alone or in combination with sulfur. [0028] There are a wide variety of vulcanization accelerators, and these are used in an amount of 0.01 to 5 parts by weight per 100 parts by weight of raw rubber, and two or more types may be used in combination. Typical vulcanization accelerators include guanidine-based, aldehyde-amine and aldehyde-ammonia-based, thiazole-based, imidacillin-based, thiourea-based, thiuram-based, dithiocarbamate-based, xanthate-based, and mixed accelerators. [0029] Vulcanization aids include metal oxides such as zinc oxide, fatty acid compounds such as stearic acid, amines, etc., and these are used in an amount of 0.1 to 10 parts by weight per 100 parts by weight of raw rubber. . Typical anti-aging agents or antioxidants added as needed are amine-based, phenol-based, phosphorus-based, sulfur-based, etc., and these are added in amounts of 0.001 to 100 parts by weight per 100 parts by weight of raw rubber. It is added in an amount of 10 parts by weight, and two or more types may be used in combination. [0030] Scorch inhibitors added as necessary include phthalic anhydride and N-nitroso-diphenylamine salicylate, and tackifiers include coumaron-indene resin,
Examples of fillers include terpene-phenolic resin, rosin ester, etc., and calcium carbonate, clay talc, and aluminum hydroxide. Furthermore, various other compounding agents may be used as necessary. [0031] The rubber composition of the present invention is produced by mixing raw rubber and various compounding agents using various mixing devices generally used for mixing rubber compositions, such as open rolls, Banbury mixer-kneader-extruders, etc. After forming into the desired shape,
Vulcanized. The rubber composition of the present invention can be used for various automobile tires, belts,
Due to its characteristics, it is suitable for use in industrial products such as hoses and anti-vibration combs, footwear, daily necessities, construction materials, and various other applications. [0032]

【Example】

Examples are shown below, but these are intended to explain the present invention more specifically and are not intended to limit the scope of the present invention. [0033]

[Reference example]

A typical example of a method for obtaining a styrene-butadiene copolymer used as component (A) and a styrene-butadiene copolymer used as component (B) in the present invention will be shown. (1) For one polymerization reactor with an inner volume of 101 cm and a polymerization stirrer of sample A-1 (Xj), the internal temperature of the polymerization reactor was maintained at 98 to 102°C, and 24 g of butadiene was added as a monomer from the bottom of the reactor. /
min and styrene at 8.5 g/min, n-hexane as a solvent at 130 g/min, tetrahydrofuran as a polar compound at 2.3 g/min, and n as a catalyst.
-Butyllithium 0.03 per 100g of monomer
6. g was continuously supplied using a metering pump to start the polymerization reaction, and the polymer solution was continuously drawn out from the top of the reactor. After reaching a steady state, 0.5 parts by weight of di-tert-butyl-p-cresol per 100 parts by weight of the polymer was added to the obtained polymer solution, and then n-hexane as a solvent was removed. The analytical values of the obtained polymer (sample A-1) are as follows:
It is shown in Table 1. [0034] The styrene content and the microstructure of the butadiene moiety were calculated by Hampton's method by measuring the spectrum using an infrared spectrophotometer. In addition, as a result of analyzing sample A-1 by G, P, and C, the weight average molecular weight (MW) was 343,000, the number average molecular weight (Mn) was 163,000, and Mw/Mn = 2.10.
Met. Note that G, P, and C are LC-1 manufactured by Shimadzu Corporation.
The detector is a differential refractometer, and the column is H2C-5.
The measurement was carried out under the following conditions: 0, 60, 70, one bottle each, temperature 40°C, and tetrahydrofuran as the solvent. [0035] (2) Using the polymerization stirrer and jacketed polymerization reactor of Sample A-2 and having an internal volume of 401 kg, 18.2 kg of cyclohexane,
Add 2.9 kg of butadiene, 1.6 kg of styrene, 7.0 g of diethylene glycol dimethyl ether, and 3.0 g of n-butyl lithium, maintain the internal temperature of the reactor at 45 to 55°C, and polymerize for 2 hours. After completion of polymerization, add the polymer solution. 3.0 g of silicon tetrachloride was added to cause a coupling reaction. After adding 0.5 parts by weight of g-tert-butyl-p-cresol per 100 parts by weight of the polymer, the solvent was removed with a heated roll to obtain sample A-2. Sample A
-2 analysis values are shown in Table 1. Also, when measured by G, P, and C, Mw=284,000Mn=164,000Mw
/Mn=1.73. [00361 (3) Sample A-9 was polymerized in the same manner as Sample A-1 except that the polar compound and catalyst amount were changed, and the weight average molecular weight (Mw) was 381,000, the number average molecular weight (Mn) was 190, 000. Mw/M
A weight A-9 with n=2.0 was obtained. Table 1 shows the analytical values of sample A-9. (4) Polymerization of Sample B-1 Using the same polymerization reactor as that used to obtain Sample A-1, the internal temperature of the polymerization reactor was maintained at 120 to 128°C, and butadiene was added as a monomer at 30.2 g/min from the bottom of the reactor. , and styrene at 2.3 g/min, n-hexane as a solvent at 13
The polymerization reaction was started by continuously feeding 0.045g of n-butyllithium as a catalyst to 100g of monomer using a metering pump, and the polymer solution was continuously fed from the top of the reactor. I pulled it out. After reaching a steady state, polymer 10 was added to the obtained polymer solution.
After adding 0.5 parts by weight per 0 parts by weight of di-tert-butyl-p-cresol, the solvent n-hexane was removed. The styrene content of the obtained polymer (sample B-1) was 7.1% by weight, and the amount of blocked styrene was 0.8% by weight.
, MW=330.000. Mn=138,000. Mw
/Mn=2.39. [0037] Table 1 shows the analytical values of the styrene-butadiene copolymer used as component (A) in the present invention together with Samples A-1 and A-2, and the analytical values of the polybutadiene copolymer used as a comparative example which is outside the scope of the present invention. Indicates the analysis value. Furthermore, Table 2 shows the analytical values of the styrene-butadiene copolymer used as component (B) of the present invention. [0038]

[Examples 1 to 3] Sample C-1 (natural rubber) Sample C-2 (polyisoprene rubber) Sample C-3 shown in Table 3 as component (C)
(polybutadiene rubber) and the aforementioned sample a-1 (polybutadiene rubber), various rubbers shown in Table 5 were used as raw material rubber, and a rubber composition was made by the compounding treatment shown in Table 4. . When the polymers shown in the examples in Table 5 were used as components (A) and (B), both (C
) The blendability with the components was good. [0039] Table 6 shows the measurement results of the reversion of vulcanization and the physical properties of the vulcanized products of these compositions. As shown in Table 6, as in Comparative Example 3, there are cases in which the styrene-butadiene copolymer (B) component and component (C) are used, and cases in which the (A) component + (B) component is used as in Comparative Example 1. When the blending amount is small, the effect of preventing the recursion of the (C) component is small, but in the compositions of Examples 1 to 3, the recursion of the (C) component is prevented. [0040] In addition, Examples 1 to 3 have better impact resilience and better impact resilience than Comparative Example 2 using the (A) component and (C) component and Comparative Example 3 using the (B) component and (C) component. Excellent balance of wet skid resistance and balance of abrasion resistance and wet skid resistance. Furthermore, in Examples 1 to 3, component (A), component (B), and (C
) is superior to the average performance of each component alone. [0041]

[Table 1]

[Table 2] [0043]

[Table 3]

[Table 4] *1 Reactant of diphenylamine and acetone

[Table 5]

[Table 6] [0047]

【Effect of the invention】

As described above, according to the present invention, a rubber composition can be obtained which has good processability, is prevented from recurving, and has improved performance such as the balance between abrasion resistance and wet skid resistance.

Claims (1)

[Claims] [Claim 1] Component (A): Obtained in an inert solvent using a polar organic compound and an organic alkali metal catalyst, the styrene content is 5 to 60% by weight, and the amount of vinyl bonds in the butadiene moiety is 35%. A styrene-butadiene copolymer having a 1,4-trans bond content of 55,000 or more and less than 350,000, a weight average molecular weight of 55,000 or more and less than 350,000, component (B): a styrene content of 5 to 40%. Styrene-butadiene copolymer in which the amount of vinyl bonds in the butadiene portion is 1% or more and less than 25% by weight, and the amount of block styrene is 5% by weight or less of the copolymer, component (C): natural rubber, polyisoprene, vinyl A rubber composition made from any one or more rubber-like polymers of polybutadiene having a bond content of 1 to 20%, and the weight ratio of components (A) and (B) to 20 to 80:80.
20. The styrene content of the polymer composition obtained by mixing components (A) and (B) is 10 to 40% by weight, the amount of vinyl bonds in the butadiene moiety is 30% or more and less than 53%, and (A)
A rubber composition in which the total amount of component (B) is 25 parts by weight or more and component (C) is 75 parts by weight or less.