JP3438318B2 - Rubber composition for tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-like polymer composition, and more specifically, it has extremely low heat build-up and significantly less rolling resistance when used for tire tread applications, and also has good wet skid performance. The present invention relates to a rubber-like polymer composition which provides a tire tread and has good processing performance.

[0002]

2. Description of the Related Art In recent years, with the development of the automobile industry, various performances such as safety, driving stability, economy, habitability, and pollution-free have been improved more than ever before with respect to tires mounted on automobiles. Is desired. In particular, the increase in consumption of petroleum-based fuels due to the increase in automobiles and the increase in air pollutants such as carbon dioxide and nitrogen oxides contained in exhaust gas have become a social problem as pollution. It has become necessary to reduce the amount of fuel consumed and to switch to electric vehicles that do not emit exhaust gas, and rubber materials that reduce rolling resistance and reduce fuel consumption have also been demanded for automobile tires.

The rolling resistance of the tire is mainly affected by the hysteresis loss of the tread during tire rotation, and the rolling resistance is improved by using a composition having less hysteresis loss. However, regarding tire performance, safety such as steering stability and braking performance on wet road surfaces (wet skid resistance characteristics), and durability such as wear resistance are also important performances. However, both rolling resistance performance and wet skid resistance performance of tires are performances related to hysteresis loss of tread rubber, and since these are contradictory, it has been conventionally difficult to improve both of them. It was However, since the vibration condition corresponding to the rolling resistance performance of the tire and the vibration condition corresponding to the wet skid resistance performance are different, pay attention to this point and
Many attempts have been made to improve the performance balance of seeds.

Many of these improvements are to improve the balance between rolling resistance and wet skid resistance of a tire by optimizing the raw material rubber used in a tire tread vulcanized rubber compound containing carbon black as a reinforcing filler. Is the way to do it. For example, JP-A-54-6224
No. 8 discloses a method of using a styrene-butadiene copolymer having a glass transition temperature of −50 ° C. or higher, a styrene content of 20 to 40%, and a vinyl bond amount of a butadiene portion of 50 to 80%. . However, when such a polymer is used, although the rolling resistance performance and the wet skid resistance performance of the tire are good, the tensile strength is low because it is high vinyl, and since a polymer having a high molecular weight is used, processing There is a problem in sex and there is a problem in industrial production.

Further, in Japanese Patent Laid-Open No. 57-55912,
A method using a styrene-butadiene copolymer having a high vinyl content and branched by a specific compound such as tin is disclosed in JP-A-59-117514, in which benzophenones are added to the polymer chain terminal. Methods using a diene polymer have been disclosed, and it has been shown that all methods have good tire rolling resistance performance and wet skid resistance performance. However, in these methods of improving rolling resistance, it has been pointed out that abrasion resistance is not always sufficient.

On the other hand, a method has recently been proposed in which by using silica instead of conventional carbon black as a reinforcing filler used in a tire tread composition, a tire having good rolling resistance and good tire performance is obtained.
Raw rubbers that match it are also shown.

[0007] When silica is used as a reinforcing filler, as a general tendency, the heat resistance and the rolling resistance performance related thereto are better as compared with the case where carbon black is used. Although the hardness and tensile strength are the same, on the other hand, there are problems such as low large deformation modulus, poor wear resistance, high viscosity of the compound, and large shrinkability of the compound and poor processability. However, in order to improve the problems of the silica compound, a method of optimizing a raw material rubber and a method of using a specific silane coupling agent to enhance the interaction between silica and rubber have been proposed.

As a method for improving the performance of a rubber composition for a tire tread using silica as a reinforcing filler by improving a raw material rubber, for example, JP-A-62-50346 discloses a diene using an organic lithium compound as an initiator. A specific (co) polymer obtained by (co) polymerizing a system monomer and then reacting the polymerization active terminal with an alkoxysilane compound having a specific structure.
A rubber composition for a tire tread using a rubber containing a polymer is disclosed, and it is shown that strength, abrasion resistance and the like are improved. Further, in JP-A-3-252433, when a (co) polymer having the above-mentioned specific structure and a glass transition temperature of -50 ° C or higher is used in a rubber composition for a tire tread, a silica filler and a specific structure are used. It has been shown that a tire having good rolling resistance performance, wet skid resistance performance, and wear resistance can be obtained by using the silane coupling agent.

US Pat. No. 5,227,425 discloses a rolling resistance performance by using a solution-polymerized SBR having a specific polymer structure and a silica filler having a specific property and specifying the kneading conditions of the rubber composition. , A method of providing a tire having improved wear resistance and wet skid resistance performance has been proposed. However, even in the technique of using the silica filler thus improved, there is a problem in that the processability is not always sufficient due to a large shrinkage of the rubber composition.

[0010]

DISCLOSURE OF THE INVENTION The present invention provides a rubber composition for a tire tread using a silica filler, which has significantly excellent rolling resistance performance, good abrasion resistance, good wet skid resistance performance, and shrinkage. It is an object of the present invention to provide a raw material rubber and a rubber composition which bring about little good processability.

[0011]

In order to achieve the above object, the present invention uses a rubber-like polymer having a specific limited polymer structure as a raw material rubber for a rubber composition for a tire tread. It is proposed to use the coalescence as a rubber composition having a specific composition.

The present invention comprises: (A) 100 parts by weight of a styrene-butadiene copolymer as a raw material rubber, which satisfies the following conditions (a) to (d):
(A) a living polymer having an active lithium terminal, which is obtained by copolymerizing styrene-butadiene in a hydrocarbon solvent using an organolithium compound as an initiator;
_(4-i) SnX _i (R is an alkyl group having 1 to 12 carbon atoms, an aryl group, i is an integer of 1 to 4 and X is chlorine or bromine);
Having a tin bond in the molecule, (b) the weight ratio of bound styrene / bound butadiene is 5/95 to 50/50 (c) Mooney viscosity (ML1 + 4,100 ° C.) is 25 to 80, (B) Reinforcement 5 to 50 parts by weight of the reinforcing silica filler (C) 5 to 50 parts by weight of the reinforcing carbon black (D) The total amount of the reinforcing silica filler and the reinforcing carbon black is 30 to 100 parts by weight (E) Silane cup 0.1 to 20 parts by weight of ring agent (F) 0.1 to 10 parts by weight of organic fatty acid (G) 1 to 50 parts by weight of extender oil (H) 1 to 5 parts by weight of vulcanizing agent And a rubber composition for a tire.

Further, in the present invention, (A-1) the styrene-butadiene copolymer satisfying the following conditions (a) to (d) is 30 to 95% by weight of the raw rubber,
(A) a living polymer having an active lithium terminal, which is obtained by copolymerizing styrene-butadiene in a hydrocarbon solvent using an organolithium compound as an initiator;
_(4-i) SnX _i (R is an alkyl group having 1 to 12 carbon atoms, an aryl group, i is an integer of 1 to 4 and X is chlorine or bromine);
It has a tin bond in the molecule, and the weight ratio of (b) bound styrene / bound butadiene is 5/95 to 50/50 (c) Mooney viscosity (ML1 + 4,100 ° C.) is 25 to 80 (A-2). One or more diene polymer rubbers selected from natural rubber, polyisoprene rubber, polybutadiene rubber or styrene-butadiene copolymer rubber having a weight ratio of bound styrene / bound butadiene of 2/98 to 50/50, 5 to 70% by weight of the raw rubber (B) 5 to 50 parts by weight of reinforcing silica filler (C) 5 to 50 parts by weight of reinforcing carbon black (D) Reinforcing silica filler and reinforcing carbon black 30 to 100 parts by weight (E) 0.1 to 20 parts by weight of silane coupling agent (F) 0.1 to 10 parts by weight of organic fatty acid (G) 1 to 50 parts by weight of extender oil for rubber. (H The vulcanizing agent is one that results in a rubber composition for a tire containing 1 to 5 parts by weight.

The present invention will be described in detail below. The styrene-butadiene copolymer rubber of the raw material rubber constituting the present invention is a rubbery copolymer obtained by copolymerizing styrene and butadiene by a solution polymerization method using an organic lithium compound as an initiator, It is a polymer rubber having a specific performance in which the reactivity of an active polymer having a lithium terminal is used to react them with an active tin compound in the course of polymerization so as to have a carbon-tin bond in the molecule.

The above-mentioned lithium-terminated active polymer is prepared by using an organolithium compound as a polymerization initiator in a hydrocarbon-based solvent such as pentane, hexane, cyclohexane, benzene and toluene, as a known typical method. Is a living polymer obtained by copolymerizing styrene and butadiene. Then, in a solution of this living polymer, a compound represented by the general formula R _(4-i) SnX _i (R is an alkyl group having 1 to 12 carbon atoms, an aryl group, i is an integer of 1 to 4, and X is chlorine or bromine) By reacting with a tin compound represented by the following, a specific styrene-butadiene copolymer rubber having a carbon-tin bond in the molecule of the present invention can be obtained. When the rubber and the filler and the like are kneaded, the carbon-tin bond in the rubber molecule is cleaved by the organic fatty acid which will be described later, and the rubber becomes active and can react with the filler and the like.

Examples of the tin compound represented by the general formula R _(4-i) SnX _i are tin tetrachloride and tin tetrabromide where i = 4, monobutyltin trichloride when i = 3 and mono. Octyl tin trichloride, i =
Examples of 2 include dibutyltin dichloride and dioctyltin dichloride, and those of i = 1 include tributyltin chloride, triphenyltin chloride and trioctyltin chloride. These tin compounds react 0.2 to 1.0 equivalent with respect to the living polymer. Among these, the use of i = 3 or 4 results in a polymer containing branched polymer molecules, which is preferable from the viewpoint of preventing cold flow of the rubber-like polymer.

Further, a tin compound with i = 3 or 4 and i =
When 1 or 2 is used in combination, the polymer contains both a polymer molecule having a branched carbon-tin bond and a polymer molecule having a linear carbon-tin bond. These tin compounds copolymerize styrene and butadiene with an organolithium compound and are added after or before the completion of the polymerization reaction. The carbon-tin bond is preferably one that can be easily cleaved by an organic fatty acid, and has both butadienyl-tin bond and styrulithium bond, but butadienyl-
The tin bond is preferable because it can be easily cleaved by an organic fatty acid.

The easiness of cleavage of the carbon-tin bond with an organic fatty acid is as follows. The cleavage reaction is carried out by adding an acid component (organic acid or inorganic acid) to a hydrocarbon solution of a rubbery polymer, and before and after the reaction. It can be confirmed by analyzing the polymer using GPC (gel permeation chromatography). It is also possible to solvent-extract the rubber component from the mixture after kneading the filler and the like as in the present invention, and similarly analyze the rubber component before and after the kneading by GPC. In any case, the GPC curve of the rubber-like polymer after reaction or kneading is preferably one having a small amount of branching components in order to achieve the effect of the present invention.

The amount of the polymer having a carbon-tin bond in the molecule is preferably 10% by weight or more of the raw rubber used in the rubber composition. In order to make the improvement of the present invention more effective, 20% by weight or more is more preferable.

Next, the weight ratio of bound styrene / bound butadiene of the styrene-butadiene copolymer of the present invention is 5 /.
It is in the range of 95 to 50/50. When the amount of bound styrene is less than 5% by weight, the tensile strength is low, and the wet skid resistance performance when used in a tire tread is insufficient, and when the amount of bound styrene exceeds 50% by weight, the hardness is increased and the tire tread composition Abrasion resistance and low temperature performance are significantly reduced.
The weight ratio of bound styrene / bound butadiene is preferably 15 / to give good fuel economy performance and tensile strength.
85/45/55, particularly preferably 25 /
It is in the range of 75 to 45/55.

If the weight ratio of bound styrene / bound butadiene is within the above range, styrene may be used in any chain form such as random, block or partial block in the molecular chain of the copolymer. However, it is preferable in terms of the rolling resistance of the composition that the block styrene in which styrene is continuous does not contain much,
The block ratio of styrene measured by the decomposition method using osmic acid or the ozone decomposition method is preferably 10% by weight or less of the amount of bound styrene, and more preferably 5% by weight or less. Further, the amount of isolated styrene measured by the ozonolysis method is preferably 50% by weight or more of the amount of bound styrene from the viewpoint of wet skid resistance performance of the composition, and the amount of the isolated styrene measured by the ozonolysis method is If the amount is 40% by weight or less of the amount of bound styrene, the wet skid resistance performance is inferior and the elastic modulus at high temperature is lowered, which is not preferable.

The microstructure of the butadiene portion of the styrene-butadiene copolymer of the present invention has a 1,2 bond content /
The molar ratio of the 1,4 bond amount is in the range of 10/90 to 85/15 because the lithium-based initiator is polymerized. There are 1,2 bond (synonymous with vinyl bond), cis-1,4 bond (synonymous with cis bond), and trans-1,4 bond (synonymous with trans bond) in the bonding mode of the butadiene moiety. The 1,4 bond amount in the invention is the total amount of the cis-1,4 bond amount and the trans-1,4 bond amount. 1,2 bond amount is 1
It is difficult to obtain a lithium-based initiator having a 1,4 bond content of more than 90% and a 1,2 bond content of more than 85% and a 1,4 bond content of less than 15% at less than 0%. In order to exhibit good fuel economy performance, the amount of 1,2 bonds is preferably 25% or more, and the amount of 1,2 bonds is 60% in order not to significantly deteriorate the strength, wear resistance and low temperature performance of the composition. The following is preferable, and 40% or less is more preferable.

Each of the bonding modes of the butadiene moiety may be one that exists uniformly in the molecular chain, or one that has various chain forms such as one that increases or decreases along the molecular chain. Further, the weight ratio of bound styrene / bound butadiene can be adjusted by adjusting the charging ratio of the monomers styrene and butadiene used. It is possible to add a polar compound such as an ether, a polyether, a tertiary amine, or a polyamine in order to set the molar ratio of 1,2 bond amount / 1,4 bond amount of the butadiene portion within the range specified in the present invention. Becomes Generally, when an organolithium compound is used as a polymerization initiator, trans-1,4 bond / cis-1,4 bond is obtained even if the amount of 1,2 bond is increased.
The bond molar ratio is almost constant, and is generally 1.3 to 1.
The range is 5.

The glass transition temperature (Tg) of the styrene-butadiene copolymer of the present invention is preferably in the range of -90 to -10 ° C. The glass transition temperature specified in the present invention is an extrapolation temperature measured using DSC. Styrene
The glass transition temperature of a butadiene copolymer is determined by the amount of bound styrene and the amount of binding mode (cis bond, trans bond, 1,2-bond) of the butadiene moiety. When the glass transition temperature is lower than -90 ° C, the wet skid performance of the tread formulation is low, while when the glass transition temperature exceeds -10 ° C, the low temperature performance and abrasion resistance are significantly deteriorated. The glass transition temperature is more preferably in the range of -75 to -20 ° C.

The Mooney viscosity (ML1 + 4,100 ° C.) of the styrene-butadiene copolymer of the present invention is in the range of 25-80 in order to maintain the heat resistance and tensile strength of the tread compound and to bring about sufficient processability. Must be If the Mooney viscosity is less than 25, heat resistance, strength and abrasion resistance are insufficient, and if the Mooney viscosity exceeds 80, workability becomes a problem. The Mooney viscosity is preferably in the range of 30 to 70.

As the polymer production process, a known method such as a batch method, a continuous method or a combination thereof can be adopted, and polymers having various molecular weight distributions obtained thereby can be used.

The molecular weight distribution (ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn)) of the styrene-butadiene copolymer rubber of the present invention is 1.05 to 4.0.
The range of 1.05 to 2.0 is preferable, especially when the rolling resistance performance is important. When the styrene-butadiene copolymer rubber of the present invention contains a branching component, the shape of the molecular weight distribution may be a polymodal shape such as bimodal or trimodal.

In the composition of the present invention, as the raw material rubber, the above specific styrene-butadiene copolymer rubber is used alone, or the above specific styrene-butadiene copolymer rubber (A-1 component) is used. ) And another specific diene polymer rubber (A-2 component) are blended and used within the range of specific conditions.

The diene polymer rubber of the component A-2 used as a blend has a weight ratio of natural rubber, polybutadiene rubber or bound styrene / bound butadiene of 2/98 to.
It is a diene polymer rubber selected from styrene-butadiene copolymer rubbers other than the A-1 component which is 50/50. Among these, as the polybutadiene rubber, a so-called low-cis polybutadiene rubber obtained by a solution polymerization method using an organic lithium compound as a polymerization initiator, a nickel polymerization initiator, a cobalt polymerization initiator, or a neodymium polymerization initiator is used. So-called high cis polybutadiene rubber can be used. As the styrene-butadiene copolymer rubber used by blending, those obtained by an emulsion polymerization method and those obtained by a solution polymerization method using an organic lithium compound as a polymerization initiator can be used.

The glass transition temperature of the component A-2 is -10 to 10.
It is preferably in the range of -20 ° C, and the Mooney viscosity (ML1 + 4,100 ° C) of the component A-2 can be 25 to 150.

In the present invention, the components A-1 and A-2 have a weight of A-1 / A-2 = 30 to 95% by weight.
Used in the range of / 70 to 5% by weight. If the amount of the component A-1 is less than 30% by weight, the rolling resistance performance will be insufficient. When the amount of the A-1 component exceeds 95 parts by weight, it becomes substantially the same as the case of the A-1 component alone.

In the rubber composition for tire tread of the present invention, 5 to 50 parts by weight of the reinforcing silica filler and 5 to 50 parts by weight of the reinforcing carbon black are used as the filler.
In addition, the total amount of the reinforcing silica filler and the reinforcing carbon black is 30 to 100 parts by weight. If the amount of the reinforcing silica filler is less than 5 parts by weight, the rolling resistance performance is not improved so much, and if it exceeds 50 parts by weight, the workability is deteriorated. If the amount of the reinforcing carbon black is less than 5 parts by weight, the conductive performance of the compound will be poor, so that the static electricity generated in the automobile cannot be grounded through the tire, and if it exceeds 50 parts by weight, the processability will be deteriorated. If the total amount of both is less than 30 parts by weight, wet skid resistance performance is not preferable and 1
If it exceeds 100 parts by weight, the rolling resistance performance is poor.

The amount of reinforcing silica filler is in the range of 10-40 parts by weight, and the amount of reinforcing carbon black is 20-60.
The range of parts by weight, and the total amount of both are preferably in the range of 30 to 70 parts by weight in applications where rolling resistance performance is particularly important. As the reinforcing silica filler used in the rubber composition of the present invention, any of wet process silica, dry process silica and synthetic silicate silica can be used. Silica with a small particle size has a high reinforcing effect, and small particles / high agglomeration type (high surface area, high oil absorption) have good dispersibility in rubber,
Particularly preferred in terms of physical properties and processability.

The reinforcing carbon black used in the rubber composition of the present invention is manufactured by the furnace method and has a nitrogen adsorption specific surface area of 50 to 200 m ² / g and DBP.
Carbon black having an oil absorption of 80 to 200 ml / 100 g is preferable, and those of FEF, HAF, ISAF, SAF class and the like can be used, and particularly high aggregation type is preferable. Further, it is also possible to use fillers such as clay, calcium carbonate and magnesium carbonate together with the reinforcing silica filler and the reinforcing carbon black as required.

Next, in the rubber-like polymer composition of the present invention, a silane coupling agent is used in order to make the coupling action (mutual coupling action) between the reinforcing silica filler and the raw material rubber close. 0.1 to 20 parts by weight is blended per part by weight.

When the amount of the silane coupling agent is less than 0.1 parts by weight, the effect of coupling is small, and when it exceeds 20 parts by weight, the reinforcing property is impaired. The amount of silane coupling agent is preferably in the range of 5 to 20% by weight of the amount of reinforcing silica filler. Examples of silane coupling agents include bis- [3- (triethoxysilyl) -propyl] -tetrasulfide, bis- [2- (triethoxysilyl) -ethyl] -tetrasulfide, 3-mercaptopropyl-
Examples thereof include trimethoxysilane, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide and 3-triethoxysilylpropylbenzothiazoletetrasulfide. In the present invention,
It is preferable to knead the silane coupling agent, the reinforcing silica filler and the raw rubber in the temperature range of 140 to 180 ° C. so that the reinforcing silica filler and the raw rubber form a sufficient bond.

Next, 0.1 to 10 parts by weight of organic fatty acid is used in the rubbery polymer composition of the present invention. The organic fatty acid is a component necessary for cutting the carbon-tin bond contained in the specific polymer of the present invention and promoting the bond between the rubber and the filler when kneading the rubber composition of the present invention. . If the organic fatty acid is less than 0.1 part by weight, the effect of breaking the carbon-tin bond is extremely small, and if the organic fatty acid exceeds 10 parts by weight, the rolling resistance performance is deteriorated.

Next, an extender oil for rubber is used in the rubbery polymer composition of the present invention, and 1 to 50 parts by weight is blended per 100 parts by weight of the rubbery polymer. The amount of extender oil for rubber is increased or decreased depending on the amount of reinforcing silica filler and reinforcing carbon black and is used to control the modulus of the vulcanized tread compound. If the amount of the extender oil for rubber is less than 1 part by weight, the elastic modulus of the tread compound will be too high and steering stability will be insufficient, and if it exceeds 50 parts by weight, the heat resistance will deteriorate. The amount of the extender oil for rubber is more preferably in the range of 3 to 20 parts by weight in applications where rolling resistance performance is particularly important.

Next, in the rubbery polymer composition of the present invention, the vulcanizing agent is used in the range of 1 to 5 parts by weight per 100 parts by weight of the rubbery polymer. Sulfur is typically used as the vulcanizing agent, and in addition, sulfur-containing compounds, peroxides and the like are used. In addition, a vulcanization accelerator such as a sulfenamide-based, guanidine-based, or thiuram-based vulcanization accelerator is used in combination with a vulcanizing agent, if necessary. If the amount of the vulcanizing agent is less than 1 part by weight, the heat resistance is poor, and if it exceeds 5 parts by weight, the elongation and strength of the composition deteriorate. Furthermore, zinc rubber, a vulcanization aid, an antiaging agent, and a processing aid are used in necessary amounts as rubber chemicals for the purpose.

In the rubbery polymer composition of the present invention, the raw material rubber, the reinforcing silica filler, the reinforcing carbon black, the silane coupling agent, the extending oil for rubber, the chemicals for rubber and the like are used by using an internal mixer or the like. Then 140-180 ° C
After kneading at a temperature of 1, the resulting composition is cooled, a vulcanizing agent such as sulfur and a vulcanization accelerator are further compounded using an internal mixer or a mixing roll, and molded into a predetermined shape. It is vulcanized at a temperature of up to 180 ° C. and exhibits its performance in the state of being a vulcanized rubber compound, and is used for a tire tread.

The rubbery polymer of the present invention is in the form of a vulcanized rubber compound containing a reinforcing silica filler and a reinforcing carbon black, and is a tire tread compound typified by high performance tires and all-season tires. Although it is suitable for use as an article, it can also be applied to other tire applications, anti-vibration rubbers, belts, hoses, industrial products, footwear, etc. by taking advantage of its characteristics.

[0042]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but these do not limit the scope of the present invention.

Reference Example SBR Production Method: An autoclave equipped with a stirrer and a jacket having an internal volume of 10 liters was used as a reactor.
540 g of butadiene, 360 g of styrene, 4900 g of cyclohexane, and 3.8 g of tetrahydrofuran as a polar substance were charged into a reactor and the temperature inside the reactor was adjusted to 65 ° C. with vigorous stirring, and then n-butyllithium was added as a polymerization initiator. The copolymerization reaction was started by adding 0.91 g. Next, when the polymerization reaction rate reached 25%, a total amount of 300 g of butadiene was continuously supplied to the reaction system at a rate of 30 g / min using a metering pump to continue the copolymerization reaction. After the supply of additional butadiene was completed, the polymerization temperature reached the maximum temperature of 97 ° C. and the copolymerization reaction was completed. Then, 0.5 equivalent of tin tetrachloride was added as a branching agent per mol of the active lithium polymer. The reaction was performed for about 10 minutes. After adding 5 g of BHT as an antioxidant to this polymer solution, the solvent was removed to obtain a styrene-butadiene copolymer rubber (Sample 1) having a target branching component.

Sample 1 was analyzed to find that the amount of bound styrene was 30%, the amount of bound butadiene was 74%, and the microscopic value of the butadiene portion calculated from the measurement results using an infrared spectrophotometer according to the Hampton method. The structure has 1,2 bonds of 3
0%, cis-1,4 binding amount 30%, trans-1,4
40% binding, Mooney viscosity (ML1 + 4,100
C) is 70, the glass transition temperature is -47 ° C, the shape of the elution curve by GPC measurement using THF as a solvent is bimodal, the amount of branched polymer determined by GPC is 50%, and the molecular weight distribution (Mw / Mn) is It was 1.7. In addition, the method of Tanaka et al. (POLYMER, vol22, 1721 (1
981)) styrene chain distribution analysis result by ozonolysis method shows that isolated styrene (S1) is 78% and long chain styrene (S8) with 8 or more styrene chains is 0%.
Met.

Sample 2 was subjected to a copolymerization reaction in the same manner as in the case of obtaining Sample 1, and then 0.4 equivalent of tin tetrachloride was added as a branching agent per 1 mol of the active lithium polymer and reacted for about 10 minutes. And 0.6 equivalent of triphenyltin chloride (TPSC) per mole of active lithium polymer.
Is a polymer obtained by reacting as a terminal functional group-providing agent.

Sample 3 was prepared in the same manner as in Sample 2 except that N-methylpyrrolidone (NM) was used as a terminal functional group-imparting agent.
It is a sample obtained using P). Sample 4 is a method in which the total amount is initially charged without adding butadiene, and tetramethylethylenediamine and potassium-ter are used as polar substances.
A copolymerization reaction was carried out using t-aminoxide (KTA) in combination, and then tin tetrachloride was obtained by a reaction with a branching agent.
Sample 5 is a method in which the total amount is initially charged without adding butadiene. For comparison, tetrahydrofuran and potassium dodecylbenzenesulphonate (DBSK) are used as a polar substance, and the reaction does not include a branched component. It is a sample of.

Sample 6 is a sample for comparison having a different molecular weight distribution obtained by a continuous polymerization method different from that of Sample 1 and containing no branching component. Sample 7 is a sample for comparison obtained by carrying out a copolymerization reaction in the same manner as in obtaining Sample 1 and then adding no branching agent. Sample 8 is a sample for comparison obtained by carrying out a copolymerization reaction in the same manner as in the case of obtaining Sample 1, and then adding silicon tetrachloride as a branching agent. The branching component of this sample is an organic fatty acid. Stable against.

Further, in the same manner as in obtaining the sample 1,
Styrene-butadiene copolymer rubbers (Samples 8 to 20) having different amounts of bound styrene, amounts of 1,2 bonds in the butadiene portion, Mooney viscosity, branched polymer amount and glass transition temperature shown in Tables 1-1 and 1-2, polybutadiene Rubber (Sample 22-
24) was adjusted. Sample 21 was obtained by a method in which the entire amount was initially charged without adding butadiene, and the copolymerization reaction was performed using tetrahydrofuran as the polar substance.

Sample 25 is a sample for comparison having a different molecular weight distribution obtained by a continuous polymerization method different from that of Sample 1 and containing no branched component. Further, commercially available styrene-butadiene copolymer rubber, polybutadiene rubber, and natural rubber shown in Table 1-3 were used as samples. The analytical values of the above samples are shown in Tables 1-1 to 1-3. The sample was analyzed by the method described below.

1) Amount of bound styrene and amount of bound butadiene A sample was used as a chloroform solution, and the amount of bound styrene [S] was determined by absorption of UV at 254 nm by the phenyl group of styrene.
(Wt%) is measured, and the amount of bound butadiene (wt%) is 1
It was calculated as 00- [S]. 2) Microstructure of butadiene part The carbon disulfide solution was used as a sample, and the infrared spectrum was measured in the range of 600 to 1000 cm −1 using a solution cell, and the microstructure of the butadiene part was calculated from the predetermined absorbance according to the calculation method of Hampton method. I asked.

3) Measured at a temperature rising rate of 10 ° C./min using a glass transition temperature DSC. The extrapolation start temperature (On setpoint) was taken as Tg.
4) Branched polymer amount GPC measurement using THF as solvent (pump: Shimadzu L
C-5A, column: 1 each for HSG-40, 50, 60,
A GPC curve by a detector (RI) was measured, and the polymer portion was used as a branched polymer, and the amount of the branched polymer was determined by the area ratio with the branched low molecular portion.

Examples 1 to 16 and Comparative Examples 1 to 17 Using the samples shown in Tables 1-1 to 1-3 as raw rubbers, Table 2
A rubber compound was obtained by the following kneading method using the compounding shown in.

[Kneading method] A pressure kneader (capacity 0.5 liter) was used. Kneading raw rubber, filler, (silica and carbon black), silane coupling agent, aromatic oil, zinc white, stearic acid (kneading time 6
Min, maximum temperature reached 170 ℃). The composition containing silica as a filler was obtained by cooling the composition obtained above to room temperature and then kneading again (kneading time 5 minutes, maximum attainable temperature 170 ° C.).
After cooling, knead the antioxidant, sulfur and vulcanization accelerator with an open roll set at 80 ° C. Mold this, 160
It was vulcanized by a vulcanizing press at 25 ° C. for 25 minutes, and the physical properties showing the following tire performances were measured.

1) Formulation Mooney Viscosity: Measured at 100 ° C. using a Mooney viscometer. The smaller the value, the better the workability. 2) Mill shrinkage: Use a 6-inch mixing roll set at 50 ° C. The roll gap is set to 0.2 mm, and it is judged by the shrinkability of the separated sheet. Good with less shrinkage.
Displayed in 4 steps of ⊚∘∘ × ∘ is the best and low shrinkage is the worst × large shrinkage 3) Hardness: Measured with JIS K6301 JIS-A hardness meter. 4) Tensile strength: Measured by the tensile test method of JIS K6301. 5) Impact resilience: JIS K6301 impact resilience is 70 ℃
Measured by. The higher the number, the better the fuel efficiency.

6) Heat resistance: Goodrich flexometer is used. Rotation speed 1800 rpm, stroke 0.
225 inches, load 55 pounds, starting temperature 50 ° C, 20
Measure the difference ΔT between the temperature in minutes and the starting temperature. 7) Wet skid resistance performance: Stanley London's portable skid tester is used to
Measured using M company's safety walk. Displayed as an index with the formulation of Comparative Example 1 as the standard. The higher the value, the better the performance. 8) Abrasion resistance: Measured using a pico abrasion tester. Displayed as an index with the formulation of Comparative Example 1 as the standard. The larger the value, the better the wear resistance. The results of performance measurement are shown in Table 3. 1 shows the balance between wet skid resistance performance and impact resilience, and FIG. 2 shows the balance between wet skid resistance performance and wear resistance.

The compositions containing a specific silica containing the styrene-butadiene copolymer rubber limited in the present invention of Examples 1 to 16 have good processability, impact resilience, heat resistance, and grip. Shows performance and wear resistance. On the other hand, Comparative Examples 2 to 6 and Sample 22 using Samples 5 to 9 having a polymer structure outside the scope of the limitation of the present invention.
The compositions of Comparative Example 7 to Comparative Example 10 using Sample 29 and Comparative Example 1 using emulsion polymerization SBR and Comparative Example 11 using natural rubber have unsatisfactory performance items and are not preferable. Comparative Example 1 in which only carbon black is mixed
Compositions 2 to 17 are poor in impact resilience and heat resistance.

Examples 17-22, Comparative Examples 18-20 Samples 1, 3, 6, 10 of the specific styrene-butadiene copolymer rubber of the present invention were used as the component (A-1), and (A-1)
-2) Using the rubbery polymers shown in Table 1-3 as the component, a rubber composition having the composition shown in Table 4 was prepared in the same manner as in Example 1, and the performance was measured. The results are shown in Table 4. Within the ranges of the types and composition ratios of the component (A-1) and the component (A-2) defined in the present invention, as shown in Table 4, a good balance of rolling resistance performance, wear resistance and wet skid resistance performance is obtained. have.

Examples 24 and 25, Comparative Examples 21 and 22 Using Sample 1 of the specific styrene-butadiene copolymer rubber of the present invention, different blending amounts such as silica blending amount and carbon black blending amount shown in Table 2 were used. A composition was obtained in the same manner as in Example 1. The results are shown in Table 5. As shown in Table 5, the composition within the range of a good composition ratio by the silica compounding amount and the carbon black compounding amount limited in the present invention has good processability, impact resilience, heat resistance, grip performance, and abrasion resistance. Showing sex.

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

[Table 3]

[0062]

[Table 4]

[0063]

[Table 5]

[0064]

[Table 6]

[0065]

[Table 7]

[0066]

[Table 8]

[0067]

EFFECTS OF THE INVENTION By using the styrene-butadiene copolymer rubber having a specific structure of the present invention in a specific composition containing a reinforcing silica filler and a reinforcing carbon black, rolling resistance performance is extremely good, grip performance, Provided is a rubber composition for a tire tread, which has good wear resistance and less shrinkage. This rubber composition for tires is useful as a material for automobile tires that require good fuel efficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing a balance between wet skid resistance performance and impact resilience.

FIG. 2 is a diagram showing a balance between wet skid resistance performance and wear resistance.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI C08K 5/09 C08K 5/09 5/541 5/54 (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 9 / 06-9/08

Claims (3)

(57) [Claims] 1. A raw material rubber comprising 10 parts of (A) a styrene-butadiene copolymer satisfying the following conditions (a) to (d):
0 part by weight, (a) a living polymer having an active lithium terminal obtained by copolymerizing styrene-butadiene in a hydrocarbon solvent using an organolithium compound as an initiator, and a general formula R _(4-i) SnX. _i (R is an alkyl group having 1 to 12 carbon atoms, an aryl group, i is an integer of 1 to 4, X is chlorine or bromine), and a carbon-tin bond obtained by the reaction with the tin compound is represented in the molecule. Have, (b) bound styrene /
Weight ratio of bound butadiene is 5/95 to 50/50
(C) Mooney viscosity (ML1 + 4,100 ° C.) is 25-
80, (B) 5 to 50 parts by weight of the reinforcing silica filler (C) 5 to 50 parts by weight of the reinforcing carbon black (D) The total amount of the reinforcing silica filler and the reinforcing carbon black is 30 to 100 parts by weight (E) 0.1 to 20 parts by weight of silane coupling agent (F) 0.1 to 10 parts by weight of organic fatty acid (G) 1 to 50 parts by weight of extender oil for rubber (H) Vulcanizing agent 1 to 5 parts by weight of a rubber composition for a tire. 2. The weight ratio of bound styrene / bound butadiene of the styrene-butadiene copolymer rubber is 25/95 to.
45/55, the molar ratio of 1,2 bond amount / 1,4 bond amount of the microstructure of the butadiene portion is 25/75 to 40/60.
The rubber composition for tires according to claim 1. 3. A raw material rubber comprising (A-1) a styrene-butadiene copolymer satisfying the following conditions (a) to (d):
To 95% by weight, (a) a living polymer having an active lithium terminal obtained by copolymerizing styrene-butadiene in a hydrocarbon solvent using an organolithium compound as an initiator, and a general formula R _(4-i). SnX _i (R is a carbon number of 1 to 1)
2 has an alkyl group, an aryl group, i is an integer of 1 to 4, X is chlorine or bromine), and has a carbon-tin bond in the molecule obtained by a reaction with a tin compound, and (b) is a bonded styrene. Weight ratio of / bound butadiene is 5/95 to 50/5
0 (c) Mooney viscosity (ML1 + 4,100 ° C) is 25
(A-2) selected from natural rubber, polyisoprene rubber, polybutadiene rubber or a styrene-butadiene copolymer rubber having a weight ratio of bound styrene / bound butadiene of 2/98 to 50/50. The above-mentioned diene polymer rubber is 5 to 70% by weight of the raw rubber, and 5 to 50 parts by weight of (B) the reinforcing silica filler (C) and 5 to 50 parts by weight of the reinforcing carbon black (D). 30 to 100 parts by weight (E) silane coupling agent 0.1 to 20 parts by weight (F) organic fatty acid 0.1 to 10 parts by weight (G) rubber A rubber composition for a tire, which comprises 1 to 50 parts by weight of an extending oil (H) and 1 to 5 parts by weight of a vulcanizing agent.