JPH07179669A - Tread rubber composition - Google Patents

Abstract

PURPOSE:To provide a tread rubber compsn. which has a good milling workability without bagging during processing thereof, and can lower the RR of a tire to enhance the grip thereof. CONSTITUTION:A tread rubber compsn. has a tandelta peak temp. (Tg) after vulcanization of -40 to +5 deg.C, and comprises the components (A), (B) and (C) (details of which are shown below) at such proportions that the component (A) accounts for 20 to 100wt.% of the components (A)+(B) and the component (C) is used in an amt. of 50 to 250 pts.wt. per 100 pts.wt. of the components (A)+(B). The component (A) is a soln.-polymerized styrene-butadiene rubber having a Mooney viscosity (ML1+4, 100 deg.C) of 30 to 200 and obtd. by copolymerizing styrene with butadiene and a polyvinyl arom. compd. and then coupling the resulting copolymer with a tri- or tetra-functional coupling agent. The component (B) is at least 1 rubber selected from the group consisting of emulsion-polymerized styrene-butadiene rubbers, butadiene rubber, natural rubber, and isoprene rubber. The component (C) is carbon black having an iodine adsorption of at least 60mg/g and an oil absorption of at least 110ml/100g.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a tread rubber composition for tires, and more particularly to a tread rubber composition for radial tires for passenger cars and racing tires.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the fuel consumption of automobiles, it is important to improve the efficiency of engines and accessories, reduce the rolling resistance (hereinafter abbreviated as RR) of tires, and reduce the weight of each component including tires. It was a challenge. In order to reduce the rolling resistance of the tire, it is most effective to reduce the energy loss of the rubber of each component constituting the tire, especially to reduce the energy loss of the tread rubber having a large capacity.

However, if natural rubber (NR) or butadiene rubber (BR) is used as a rubber component in order to reduce energy loss of the tread rubber, the RR is lowered, but at the same time, the wet grip is also lowered. Therefore, recently, by using a styrene-butadiene rubber (hereinafter referred to as SBR) obtained by solution polymerization in which the amounts of styrene and vinyl are adjusted to specific ranges, RR is lowered and wet grip is maintained or improved. It has become possible to

Recently, with the development of engines and weight reduction of automobiles, and the development of automobiles having low fuel consumption and high performance, the automobiles have low RR, high grip, and high steering stability. Tires are becoming more demanding. In such a case, in order to obtain high grip, a solution-polymerized SBR having a higher tan δ peak temperature (T _g ) is used, and a carbon black having low energy loss is used. Particularly in racing tires that must maintain a high grip performance stably until the latter half of the race, a large amount of process oil such as aroma oil is added in addition to the solution-polymerized SBR having a high T _g and carbon black.

[0005]

However, when a solution-polymerized SBR having a high T _g is used in combination with carbon black having a low energy loss, the heating roll is used during the processing step, particularly when the heating is performed before the tread rubber is extruded. (Road mill,
Surge mill and feed mill) have a problem that bagging (a phenomenon in which rubber wound around a roll is lifted from the roll surface to make it impossible to insert a knife or feed a rubber) occurs. If this bagging occurs, it may be difficult to supply rubber to the tread extruder, and it may be impossible to manufacture a tire.

Further, since a large amount of process oil is blended in a racing tire, the torque in the Banbury mixer does not increase during kneading, and carbon black and other dispersion defects are likely to occur. Although this point has conventionally been dealt with by performing remilling, a decrease in productivity cannot be avoided.

The present invention has been made in view of these problems, and an object of the present invention is to provide a tread rubber composition which can lower the RR of a tire and enhance grip, and which does not cause bagging during processing, and kneading. It is an object of the present invention to provide a tread rubber composition that gives a racing tire having excellent workability and high grip.

[0008]

The object of the present invention is obtained by copolymerizing styrene, butadiene and a polyvinyl aromatic compound and further coupling them with a coupling agent having a functionality of 3 to 4 to give Mooney. Viscosity (ML
_{1 + 4} , 100 ° C.) is 30 to 200, and at least one selected from the group consisting of component (A) consisting of solution-polymerized styrene-butadiene rubber, emulsion-polymerized styrene-butadiene rubber, butadiene rubber, natural rubber and isoprene rubber.
Component (B) consisting of seed rubber and iodine adsorption of 6
The component (C) is composed of carbon black having an oil absorption of 110 ml / 100 g or more at 0 mg / g or more, and the proportion of the component (A) in the component (A) + component (B) is 20 to 100% by weight. And the component (C) is 50 to 250 parts by weight, and the tan δ peak temperature (T _g ) after vulcanization is −4 when the amount of the component (A) + component (B) is 100 parts by weight.
Achieved by a tread rubber composition that is 0 to + 5 ° C.

[0009]

FUNCTION AND EXAMPLE The tread rubber composition of the present invention comprises
Consisting of the above components (A), (B) and (C),
Further, other additives are blended. According to the present invention, by combining the above components, a tread rubber composition that has good workability without bagging, and can reduce the RR of a tire and enhance grip can be obtained.

The component (A) can be obtained by copolymerizing styrene, butadiene and a polyvinyl aromatic compound, and further coupling them with a coupling agent having a functionality of 3 to 4. More specifically, for example, it is optimally manufactured by the following method. First, an organic lithium compound is present as a polymerization initiator in a hydrocarbon solvent, and styrene, butadiene, and a polyvinyl aromatic compound are copolymerized to obtain a copolymer having lithium at the terminal of the copolymer. Then, a solution polymerization SBR is obtained by adding a coupling agent having a functionality of 3 to 4 to cause a coupling reaction. The total amount of the polyvinyl aromatic compound may be added at the initial stage of the polymerization, or may be sequentially added during the polymerization, and a part of the polyvinyl aromatic compound may be used after the coupling reaction with the trifunctional or tetrafunctional coupling agent. .

Examples of the polyvinyl aromatic compound include divinylbenzene, 1,2,4-trivinylbenzene, 1,3,5-trivinylbenzene, 1,3-divinylnaphthalene, 1,8-divinylnaphthalene, and , 2
-Divinyl-3,4-dimethylbenzene, 2,4-divinylbiphenyl, 3,5,4'-trivinylbiphenyl and the like can be mentioned, and one or more of these can be used. Of the above compounds, divinylbenzene is preferable from the viewpoint of industrial availability, and industrially available mixtures of ortho, meta and para forms thereof are used.

The amount of the polyvinyl aromatic compound used is usually 0.05 to 0.05 with respect to the organolithium compound which is a polymerization initiator.
It is 1.0 times mol, preferably 0.1 to 0.6 times mol. If the amount used is too small, the resulting copolymer will have an unfavorable molecular weight distribution and the processability of the copolymer will deteriorate. On the other hand, if the amount used is too large, the viscosity of the polymerization solution will remarkably increase, controllability during production will be poor, and undesirable side reactions such as gelation will occur.

Examples of the trifunctional or tetrafunctional coupling agents include silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, germanium tetrachloride, tin tetrachloride, methyltrichlorosilane, butyltrichlorotin and bistrichlorosilylethane. , Bistrichloroethane, etc., and silicon tetrachloride or tin tetrachloride are preferable from the viewpoint of reactivity and industrial availability.

The amount of the trifunctional or tetrafunctional coupling agent used is usually 0.03 to 0.3 times by mole, preferably 0.05 to 0.2, with respect to the organolithium compound which is a polymerization initiator.
It is twice the mole. If the amount used is too small, the resulting copolymer will have an unfavorable molecular weight distribution and the processability of the copolymer will deteriorate. On the other hand, if the usage is excessive,
It is economically disadvantageous because the effect of improving the workability with respect to the increase in the amount used is saturated.

The Mooney viscosity (ML _{1 + 4} ) of the component (A),
(100 degreeC) is 30-200, Preferably it is 40-150. If the viscosity is too high, the mixed state tends to deteriorate when the rubber composition is obtained by blending the additive,
If it becomes too low, the impact resilience properties and wear resistance of the tread rubber tend to deteriorate.

Solution polymerized SBR which is the component (A) of the present invention
The bound styrene content is preferably 5 to 60% by weight, more preferably 10 to 50% by weight. Particularly preferably, the amount of bound styrene is 15 to 50% by weight, and further 15
-40% by weight is preferred. If the amount of bound styrene is too small, the wet grip tends to deteriorate, and if it is too large, the RR and low temperature specification tend to deteriorate.
When used for racing tires, the amount of bound styrene is preferably 20 to 60% by weight, more preferably 20 to 50% by weight, and further preferably 25 to 45% by weight. If too small, the grip during race running deteriorates, If it becomes too large, the grip performance and wear resistance at the beginning of running tend to deteriorate.
The amount of bound styrene was measured by the refractive index method.

The solution-polymerized SBR preferably has a vinyl content in the butadiene portion of 10 to 80 mol%. More preferably, the vinyl content is 20 to 70 mol%,
In particular, it is 20 to 60 mol%. If the vinyl content is too low, the wet grip and grip during race running tend to be inferior, and if it is too high, the strength of the tread decreases and wear resistance deteriorates, and further industrial production tends to be difficult. . The vinyl content is calculated by infrared spectroscopy.

In order to adjust the vinyl content of the butadiene part, various compounds can be used as the Lewis basic compound. However, ether compounds and tertiary amines are preferable in view of industrial availability. preferable. Examples of ether compounds include cyclic ethers such as tetrahydrofuran, tetrahydropyran, and 1,4-dioxane; aliphatic monoethers such as diethyl ether and dibutyl ether; ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl. ether,
Aliphatic polyethers such as diethylene glycol dibutyl ether; aromatic ethers such as diphenyl ether and anisole. Examples of the tertiary amine compound include triethylamine, tripropylamine, tributylamine, N, N, N ',
Examples thereof include N'-tetramethylethylenediamine, N-diethylaniline, pyridine and quinoline. The polymerization temperature at the time of solution polymerization may vary depending on the target microstructure, but is preferably 0 to 150 ° C., more preferably 30 from the viewpoints of economic efficiency and the presence or absence of side reactions.
~ 80 ° C.

In the tread rubber composition of the present invention, the solution-polymerized SBR has three or more peaks in the molecular weight distribution curve (the vertical axis is the weight fraction, the horizontal axis is the molecular weight) obtained by high performance liquid chromatography. However, in the range of 100,000 or more in terms of standard polystyrene equivalent, the weight ratio of the high molecular weight molecular chain having a molecular weight of 5 times or more the peak located on the lowest molecular weight side to the whole copolymer is 5 to 60%. Those are preferable. The three or more peaks of the molecular weight distribution curve may be located anywhere, and the number and position of the peaks are controlled by the amounts of coupling agent and polyvinyl aromatic compound. The weight ratio is more preferably 10 to 40%. If this weight ratio is too large or too small, the workability tends to deteriorate. Further, if the number of peaks in the molecular weight distribution curve is less than 3, the effect of improving the workability is not recognized.

The component (A) constitutes 20 to 100% by weight, preferably 30 to 100% by weight, more preferably 40 to 100% by weight of the rubber component, that is, the components (A) + (B). When the ratio of the component (A) becomes too small,
There is a tendency that the wet grip, the grip during race running, and the RR deteriorate, and the balance between the dispersibility of carbon black and the grip and the grip deteriorates.

Component (B) is at least one selected from the group consisting of emulsion-polymerized SBR prepared by a conventional method, butadiene rubber, natural rubber and isoprene rubber,
It may be a mixture of two, three or all.

The component (B) is 80 to 0% by weight of the rubber component, preferably 70 to 0% by weight, more preferably 60.
~ 0% by weight. When the component (B) is not included, the present invention also includes it.
A more remarkable effect on workability is recognized. If the proportion of the component (B) becomes too large, the balance between the grip and the grip during running the race, the dispersibility of RR and carbon black and the grip tends to be deteriorated.

Component (C) has an iodine adsorption amount of 60 mg /
g or more, preferably 100 mg / g or more and 250 mg / g
g or less, preferably 150 mg / g or less, and oil absorption of 110 ml / 100 g or more, preferably 250 ml / g
The carbon black is 100 g or less, particularly 160 ml / 100 g or less. When the amount of iodine adsorbed is less than 60 mg / g, the reinforcing property is reduced, the wear resistance of the tread is reduced, the grip performance is reduced, and the oil absorption is 110 ml.
If it is less than 100 g, the RR and wear resistance of the tire tend to deteriorate. For racing tires, the iodine adsorption amount is 100 mg / g or more, preferably 120 to 2
The oil absorption of 50 mg / g is 110 ml / 100 g or more, preferably 110 to 250 ml / 100 g.

The component (C) carbon black is
N351, N339, N220, N234, N110 and the like can be used, and N220 and N110 are suitable for racing tires.

Component (C) is the total rubber component (component (A)
+ (B)) It is 50 to 250 parts by weight with respect to 100 parts by weight, and is 50 to 130 parts by weight, especially 55 to 50 parts for passenger cars.
110 parts by weight is preferable, and for racing, 55 to 170 parts by weight is preferable. If the amount is less than 50 parts by weight, the abrasion resistance of the tread tends to decrease,
When the amount is more than the weight part, the RR of the tire is deteriorated and the kneading work tends to be difficult.

Other additives include vulcanizing agents such as sulfur, vulcanizing aids such as zinc white and stearic acid, and accelerator C.
Vulcanization accelerators such as Z (N-cyclohexyl-2-benzothiazylsulfenamide) and accelerator NS (Nt-butyl-2-benzothiazylsulfenamide), old protection 1
3 (N, N'-diphenyl-p-phenylenediamine), anti-aging agent such as IPPD (N-isopropyl-N'-phenyl-p-phenylenediamine), aromatic oil, naphthene oil, paraffin oil, etc. Process oil or the like is used. The blending amount of these additives is not particularly limited, but the RR of the tire is reduced,
The compounding is carried out within a range that does not impair the object of the present invention of enhancing grip and preventing bagging during processing.
Although a large amount of process oil is used for racing tires, the composition of the present invention improves kneading work and eliminates the need for remilling.

Unvulcanized rubber can be obtained by mixing and stirring the above-mentioned components (A), (B) and (C) and other additives by a conventional method. A tread is obtained by molding this unvulcanized rubber into a predetermined shape and vulcanizing it. In the tread rubber composition of the present invention, after vulcanization,
That is, the T _g of the vulcanized rubber composition is −40 to + 5 ° C.
Is. Low temperature properties, such as after vulcanization a T _g tends to grip inferior when from lower the wet grip and racing cars -40 ° C., + 5 higher than ° C. When the grip performance on snow surface abrasion resistance and winter running Initial grip performance tends to deteriorate. T _g for normal radial tires
Is −40 to −5 ° C., preferably −35 to −5 ° C.,
The stress retention before vulcanization, that is, the stress retention of the unvulcanized rubber obtained by mixing and stirring is 50% or more, preferably 50 to 100%. The stress retention rate before vulcanization is 5
If it is less than 0%, bagging on the roll becomes more intense,
Feeding into the extruder tends to be difficult. Further, _{T g} is -25 to + 5 ° C. In a racing tire, preferably -
20 to -5 ° C.

The stress retention of unvulcanized rubber is measured by the following method.

First, unvulcanized rubber was calendered into a sheet having a thickness of 2 mm, the sheet was punched out with a JIS No. 1 dumbbell, and then subjected to a tensile test under the conditions of a temperature of 70 ° C., a pulling speed of 500 mm / min and an initial elongation of 20%. After that, the stress relaxation was measured, and the stress maximum value (σ _Max ) and the maximum value were measured and then 3
The ratio with the stress value after 2 seconds (σ ₃ ) was defined as the stress retention rate.

Stress retention rate (K _s ) = (σ ₃ / σ _Max ) × 100% Further, the tan δ peak temperature T _{g after} vulcanization was measured using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. A tan δ temperature dispersion curve is obtained by measurement under the conditions of 10 Hz, initial strain of 10%, amplitude of ± 0.25%, and heating rate of 2 ° C./min, and the temperature at which the peak value is shown is obtained.

The tread rubber composition of the present invention is usually prepared by first adding an additive other than the vulcanizing agent and the vulcanization accelerator, the component (A),
The components (B) and (C) are kneaded at the base using a Banbury mixer, and then the vulcanizing agent and the vulcanization accelerator are mixed.

The tread rubber composition thus prepared is molded into a predetermined shape and vulcanized to produce a tread, and the tire tread composition of the present invention is characterized by undergoing a general tire manufacturing process. A tire having is obtained.

The present invention will be described below with reference to specific examples, but the present invention is not limited to these.

Example 1 1,3-Butadiene, styrene, n-hexane, tetrahydrofuran, n-butyllithium and divinylbenzene were charged in a predetermined amount, a polymerization reaction was carried out, and silicon tetrachloride was used as a coupling agent with stirring. By performing the coupling reaction while performing, the amount of bound styrene is 30
A solution-polymerized SBR having a vinyl content of 40 mol% in the butadiene portion was prepared by weight. High performance liquid chromatography (by HLC-TWINCLE manufactured by JASCO Corporation)
From the molecular weight distribution curve obtained by
And the weight ratio of the high molecular weight molecular chain having a molecular weight of 5 times or more of the standard polystyrene reduced molecular weight corresponding to the peak located on the lowest molecular weight side to the whole copolymer is 3
It was 0%. Mooney viscosity of this solution-polymerized SBR (Moonie Viscometer SMV201 manufactured by Shimadzu Corporation)
Was 60. The divinylbenzene used is a mixture of ortho, meta and para forms.

A tread rubber composition was prepared by kneading the solution-polymerized SBR with the other components and additives shown in Table 1 using a Banbury mixer.

This tread rubber composition was treated with Triple BO
A steel radial tire (195 / 65R15) was produced by extrusion with an X-type extruder.

Table 2 shows the results of testing the tread rubber composition and the tire as described above for the following items.

Stress retention (%) of unvulcanized rubber: According to the above-mentioned measuring method.

Tan δ peak temperature T after vulcanization
_g (° C.): According to the measuring method described above.

Mill bagging during extrusion: It was confirmed whether bagging occurred during tire production.

Rolling resistance (RR): Using a uniaxial drum tester, a speed of 80 km / h, an internal pressure of 2.0 kg / cm ² ,
The measurement was performed under a load of 400 kg. The results are represented by an index with Comparative Example 3 as a reference (100). The smaller the value, the better the rolling resistance.

Wet grip: The manufactured steel radial tire was mounted on a new car with a displacement of 2000 cc, and the vehicle was running on an Alfalto road surface at a speed of 40 km / h to 20 km / h.
The deceleration is calculated from the time required to decelerate to / h, and the result is represented by an index with Comparative Example 3 as a reference (100). The larger this value, the better the wet grip.

Examples 2 to 5 Under the conditions shown in Table 1, a tread rubber composition was prepared in the same procedure as in Example 1, and a steel radial tire (195
/ 65R15) was produced. The tread rubber composition and tire were tested for the same items as in Example 1. The results are shown in Table 2.

Comparative Examples 1 to 6 Under the conditions shown in Table 1, a tread rubber composition was prepared in the same procedure as in Example 1, and a steel radial tire (195
/ 65R15) was produced. The tread rubber composition and tire were tested for the same items as in Example 1. The results are shown in Table 2. Comparative Example 3 uses an emulsion-polymerized SBR which has been most often used in the past, and does not cause bagging during processing, and thus was used as a reference for expressing performance.

[0045]

[Table 1]

[0046]

[Table 2]

* 1 to * 7 in the table are annotated as follows.

* 1: Number of peaks of molecular weight distribution curve obtained by high performance liquid chromatography (vertical axis is weight fraction, horizontal axis is molecular weight) * 2: Lowest molecular weight of molecular weight distribution curve obtained by high performance liquid chromatography Polymerization ratio (%) of the high molecular weight chain having a molecular weight of 5 times or more of the standard polystyrene-equivalent molecular weight corresponding to the peak located on the side relative to the entire copolymer * 3: N, N'-diphenyl-p-phenylenediamine * 4 : N-cyclohexyl-2-benzothiazyl sulfenamide * 5: SBR1712 (bound styrene content 23.5% by weight, vinyl content 18 mol%, oil extension 37.5 phr
(Rubber of component (B)) * 6: Emulsion polymerization SBR (35% by weight of bound styrene, vinyl content 18 mol%, oil extension 37.5 phr (rubber of component (B))) * 7: Emulsion polymerization SBR (bound styrene content 45% by weight, vinyl content 18 mol%, oil extension 37.5 phr (based on rubber of component (B))) Regarding the data in Tables 1 and 2, the following can be said.

Comparative Example 1 Solution-polymerized SBR was used, but no polyvinyl aromatic compound was used, so bagging occurs.

Comparative Example 2 Since the T _g is low, the wet grip is significantly inferior.

Comparative Example 4 RR is greatly inferior because T _g is high.

Comparative Example 5 The same solution-polymerized SBR as in Example 1 containing divinylbenzene was used as the solution-polymerized SBR, but the RR was inferior because the compounding amount was small.

Comparative Example 6 As in Comparative Example 5, the same solution-polymerized SBR as in Example 1 was used, but the amount of carbon blended was large, the stress retention of unvulcanized rubber was small, and bagging occurred. RR
Is also unfavorable.

Example 1 Although the bound styrene content and vinyl content were close to those in Comparative Example 1, since divinylbenzene was included in the molecular chain, the stress retention of the unvulcanized rubber was as high as 55% and bagging occurred. Without it, both RR and wet grip are superior to Comparative Example 3.

Examples 2, 4, and 5 are examples in which the emulsion-polymerized SBR of the component (B), polybutadiene, and natural rubber were blended, respectively.

Example 3 This is an example using a solution-polymerized SBR having a relatively high T _g and is particularly excellent in wet grip.

Example 6 1,3-Butadiene, styrene, n-hexane, tetrahydrofuran, n-butyllithium and divinylbenzene were charged in predetermined amounts to carry out a polymerization reaction. Using silicon tetrachloride as a coupling agent, stirring was performed. By conducting the coupling reaction while performing, the amount of bound styrene was 35
A solution-polymerized SBR having a vinyl content of 45 mol% in the butadiene part was prepared by weight. High performance liquid chromatography (by HLC-TWINCLE manufactured by JASCO Corporation)
From the molecular weight distribution curve obtained by
And the weight ratio of the high molecular weight molecular chain having a molecular weight of 5 times or more of the standard polystyrene reduced molecular weight corresponding to the peak located on the lowest molecular weight side to the whole copolymer is 3
It was 0%. Mooney viscosity of this solution-polymerized SBR (Moonie Viscometer SMV201 manufactured by Shimadzu Corporation)
Was 55). The divinylbenzene used is a mixture of ortho, meta and para forms.

A tread rubber composition was prepared by kneading the solution-polymerized SBR with the other components and additives shown in Table 3 using a Banbury mixer.

Using this tread rubber composition, a slick tire for racing (front 10 × 3.60-5,
Rear 11x6.00-5) was produced.

Table 4 shows the results of testing the tread rubber composition and the tire as described above with respect to the following items.

Torque (index) in Banbury mixer:
The torque applied to the rotor when the tread rubber composition was kneaded with a Banbury mixer was measured, and the torque in Example 6 was set to 100 and evaluated by an index.

Tan δ peak temperature Tg after vulcanization
(° C): Same as above.

Carbon dispersibility (%): The dispersion state of carbon black in the rubber after vulcanization is determined by the Dunlop method (Lei).
Also called the gh-Dugmore method. ) (See "Rubber Society of Japan" No. 4 (1968)).

Grip performance (index): The produced slick tire was mounted on a racing cart with a displacement of 100 cc, and the circuit was run for 7 laps on a circuit of 1013 m for 1 lap, and the grip was sensory evaluated. The grip during traveling for 2 to 4 laps was defined as the first half grip, and the grip during traveling for 5 to 7 laps was defined as the latter half grip.

Examples 7 to 9 and Comparative Examples 7 to 11 Under the conditions shown in Table 3, a tread rubber composition was prepared in the same procedure as in Example 6 to prepare slick tires. The tread rubber composition and tire were tested for the same items as in Example 6. The results are shown in Table 4.

[0066]

[Table 3]

[0067]

[Table 4]

* 8 and * 9 in Table 3 are annotated next.

* 8: Nt-butyl-2-benzothiazolylsulfenamide * 9: SBR NIPOL 9520 (emulsion-polymerized SBR manufactured by Nippon Zeon Co .; bound styrene content 45.0% by weight, vinyl content) 18 mol%, oil extension 37.5 phr
(Rubber Criterion for Component (B)) The following can be said with respect to the data in Tables 3 and 4.

Comparative Example 7 Although the solution-polymerized SBR was used, but the polyvinyl aromatic compound was not used, the torque in the Banbury mixer was low and the carbon dispersion was poor. The grip is also lower than that of the sixth embodiment.

Comparative Example 8 The same solution-polymerized SBR as in Example 6 containing divinylbenzene was used as the solution-polymerized SBR, but since the blending amount was small, the durability of the grip was poor and the latter half grip was low.

Comparative Example 9 Since emulsion-polymerized SBR was used, the same procedure as in Comparative Example 8 was performed.
The grip in the second half is poor.

Comparative Example 10 The grip is poor because the T _g is low.

Comparative Example 11 Since T _g is high, the grip in the first half is poor.

Example 6 Although the bound styrene amount and vinyl content were close to those in Comparative Example 7, since divinylbenzene was included in the molecular chain, torque in the Banbury mixer was high and carbon dispersion was good. The grip is also good.

Examples 7 to 9 These are examples in which the emulsion-polymerized SBR of component (B), polybutadiene, and natural rubber were mixed, respectively, and both high torque in the Banbury mixer and good grip performance were obtained.

[0077]

As described above, the tread rubber composition of the present invention can reduce the rolling resistance of the tire and enhance the grip, and it does not cause bagging during processing. It also facilitates the kneading operation and improves the dispersibility of carbon black and the like.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Imaoka 1-1-1 Tsutsui-cho, Chuo-ku, Kobe-shi, Hyogo Sumitomo Rubber Industries, Ltd. (72) Inventor Keisaku Yamamoto, 5 on Anezaki Kaigan, Ichihara-shi, Chiba 1 Sumitomo Chemical Co., Ltd. (72) Inventor Tsukasa Wakatsuki 1-5, Anesaki coast, Ichihara city, Chiba Sumitomo Chemical Co., Ltd. (72) Kouji Tsuji, 1-5 Anezaki coast, Ichihara, Chiba Sumitomo chemical Within Kogyo Co., Ltd.

Claims (6)

[Claims] 1. Obtained by copolymerizing styrene, butadiene and a polyvinyl aromatic compound and further coupling them with a coupling agent having a functionality of 3 to 4, and having a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 30. ~ 2
Component (A) consisting of solution-polymerized styrene-butadiene rubber which is 00, component (B) consisting of at least one rubber selected from the group consisting of emulsion-polymerized styrene-butadiene rubber, butadiene rubber, natural rubber and isoprene rubber,
And iodine adsorption amount of 60 mg / g or more and oil absorption amount of 11
The component (C) is composed of 0 ml / 100 g or more of carbon black, and the proportion of the component (A) in the component (A) + component (B) is 20 to 100% by weight. The component (C) is 50 to 250 parts by weight when the component (B) is 100 parts by weight, and the tan δ after vulcanization is
A tread rubber composition having a peak temperature (T _g ) of -40 to + 5 ° C. 2. Obtained by copolymerizing styrene, butadiene and a polyvinyl aromatic compound and further coupling them with a coupling agent having a functionality of 3 to 4, and having a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 30. ~ 2
Component (A) consisting of solution-polymerized styrene-butadiene rubber which is 00, component (B) consisting of at least one rubber selected from the group consisting of emulsion-polymerized styrene-butadiene rubber, butadiene rubber, natural rubber and isoprene rubber,
And iodine adsorption amount of 60 mg / g or more and oil absorption amount of 11
The component (C) is composed of 0 ml / 100 g or more of carbon black, and the proportion of the component (A) in the component (A) + component (B) is 20 to 100% by weight. When the component (B) is 100 parts by weight, the component (C) is 50 to 130 parts by weight, the stress retention rate before vulcanization is 50% or more, and the tan δ peak temperature (T _g ) after vulcanization is A tread rubber composition having a temperature of -40 to -5 ° C. 3. The tread rubber composition according to claim 2, wherein the solution-polymerized styrene-butadiene rubber has a bound styrene content of 5 to 50 wt% and a vinyl content of the butadiene portion of 10 to 80 mol%. 4. A copolymer obtained by copolymerizing styrene, butadiene and a polyvinyl aromatic compound, and further obtained by coupling with a coupling agent having a functionality of 3 to 4 and having a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 30. ~ 2
Component (A) consisting of solution-polymerized styrene-butadiene rubber which is 00, component (B) consisting of at least one rubber selected from the group consisting of emulsion-polymerized styrene-butadiene rubber, butadiene rubber, natural rubber and isoprene rubber,
And the iodine absorption is 100 mg / g or more and the oil absorption is 1
10 ml / 100 g or more of the component (C) made of carbon black is contained, and the ratio of the component (A) in the component (A) + component (B) is 20 to 100% by weight,
When component (A) + component (B) is 100 parts by weight, component (C) is 50 to 250 parts by weight, and tan δ after vulcanization
A tread rubber composition having a peak temperature (T _g ) of −25 to + 5 ° C. 5. The tread rubber composition according to claim 4, wherein the solution-polymerized styrene-butadiene rubber has a bound styrene content of 20 to 60% by weight and a vinyl content of the butadiene portion of 20 to 80 mol%. 6. The solution-polymerized styrene-butadiene rubber has a molecular weight distribution curve of 3 or more peaks obtained by high performance liquid chromatography, and has a standard polystyrene equivalent molecular weight of 5 corresponding to the peak located on the lowest molecular weight side. The tread rubber composition according to claim 1, 2, 3, 4, or 5, wherein the weight ratio of the high molecular weight molecular chain having a double or more molecular weight to the whole copolymer is 5 to 60%.