JPH0977912A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for tire treads, suitable for use in the production of tires having increased resistance to wet skid, reduced rolling resistance and improved low-temperature brittleness without detriment to high- temperature elongation. SOLUTION: This rubber composition for tire treads comprises 100 pts.wt. rubber component containing a terminal-modified solution-polymerized styrene/ butadiene copolymer rubber(SBR) (A) and a diene rubber (B) other than component A and 30-80 pts.wt. at least one reinforcing filler selected between carbon black and silica, the reinforcing filler being unevenly distributed in components A and B so that the relationship: 0<CA/CB<1 may be held (wherein CA is the concentration of the filler in component A, and CB is that of the filler in component B).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for use in the production of tires having increased wet skid resistance, reduced rolling resistance and improved low temperature embrittlement without impairing high temperature elongation. The present invention relates to a rubber composition for a tire tread.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for resource saving in the industrial world, and the tire industry is also required to develop a tire having improved wet grip performance and rolling resistance. Based on these demands,
For example, JP-A-57-195636 and JP-A-6-3
Various proposals have been made such as 2943 and Japanese Patent Laid-Open No. 6-80786. On the other hand, as a response to the market where the operating temperature range is low, from the viewpoint of low temperature embrittlement and productivity,
Demands for improving tire performance such as elongation characteristics at high temperatures have been diversified, and it has been difficult for the conventional technology to satisfy all these demands.

[0003]

Accordingly, the present invention is used for producing a tire having increased wet skid resistance, reduced rolling resistance and improved low temperature embrittlement without impairing high temperature elongation. An object of the present invention is to provide a rubber composition for a tire tread, which is suitable for

[0004]

According to the present invention, (i)
100 parts by weight of a rubber component containing (A) end-modified solution-polymerized styrene / butadiene copolymer rubber (SBR) and (B) a diene rubber other than SBR, and (ii) at least one selected from carbon black and silica the ratio of reinforcing filler concentration C _B in the reinforcing filler concentration C _a and the rubber component of 30 to 80 parts by weight reinforcing filler in the rubber component (a) (B) is 0 <C _a / C _B < Provided is a rubber composition for a tire tread, which is unevenly distributed in a rubber component so that the rubber composition has a composition of 1.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The rubber component of the rubber composition for a tire tread according to the present invention is composed of (A) a terminal-modified solution-polymerized styrene / butadiene copolymer rubber (SBR) and (B) a diene rubber other than the SBR.

The end-modified solution-polymerized SBR (end-modified S-SBR) which is the first component (A) of the rubber component has a styrene content of 10 to 25% by weight and a vinyl content of 50 to 8%.
A 0% by weight solution-polymerized SBR which is end-modified according to a conventional method is used. As the terminal modification method, for example, the method disclosed in JP-A-63-150338 can be used. More specifically, the terminal modification is, for example, SBR.
The atomic group of the following formula is introduced at the end of.

[0007]

Embedded image

This atomic group is> C (M) N <(wherein M
A compound having an O or S atom) is added to a solution in which the polymerization reaction is completed or a solution in which SBR is dissolved in a suitable solvent in the presence of an alkali metal-based catalyst such as n-butyllithium. , SBR can be introduced at the end of SBR. Here, as the above compound, N, N-dimethylformamide, N, N
-Diethylformamide; N, N-diethylacetamide; aminoacetamide, N, N-dimethyl-N ',
N'-dimethylaminoacetamide, N-phenyldiacetamide; N, N-dimethylacrylamide, N, N
-Dimethylmethacrylamide; propionamide,
N, N-dimethylpropionamide; 4-pyridylamide, N, N-dimethyl-4-pyridylamide; N, N-
Dimethylbenzamide, p-aminobenzamide,
N ', N'-(p-dimethylamino) benzamide,
N, N-dimethyl-N '-(p-ethylamino) benzamide; N-acetyl-N-2-naphthylbenzamide; nicotinamide, N, N-diethylnicotinamide; succinic acid amide, maleic acid amide, N, N ，
N ', N'-tetramethylmaleic acid amide; succinimide, maleimide, N-methylmaleimide, N-methylphthalimide, 1,2-cyclohexanecarboximide, N-methyl-1,2-cyclohexanedicarboximide; oxamide, 2 -Flamid, N, N, N ', N'
-Tetramethyloxamide, N, N-dimethyl-2-furamide; N, N-dimethyl-8-quinolinecarboxamide; N, N-dimethyl-p-amino-benzalacetamide, N, N-dimethyl-N '. , N '-(p'-dimethylamino) cinnamylidene acetamide; N, N-dimethyl-N', N '-(2-dimethylamino) vinylamide; N'-(2-methylamino) vinylamide; urea, N , N'-dimethylurea, N, N, N ', N'-tetramethylurea; methyl carbamate; methyl N, N-diethylcarbamate; ε-caprolactam, N-methyl-ε-caprolactam, N-acetyl- ε-caprolactam, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, 2-piperidone,
N-methyl-2-piperidone, 2-quinoline, N-methyl-2-quinoline, 2-indolinone, N-methyl-2
-Indolinone; isocyanuric acid, N, N ', N'-trimethylisocyanuric acid, and the like, and corresponding sulfur-containing compounds thereof. Among them, particularly preferred compounds are
Examples thereof include compounds in which an alkyl group is bonded to nitrogen. The rate of terminal modification is preferably 30 to 80%.

As the second component (B) of the rubber component,
Any diene rubber other than the terminal-modified S-SBR of the first component, such as natural rubber (NR), polybutadiene rubber (BR), any styrene-butadiene copolymer rubber (SBR), conjugated diene-unsaturated nitrile. Examples thereof include copolymer rubber (NBR).

According to the present invention, the rubber components (A) and (B) are (A) / (B) (weight ratio) 75/25 to 55.
/ 45 is preferable, and 75/25 to 60/40 is more preferable. If the proportion of the component (A) in the rubber component is small (that is, if the proportion of the component (B) is large), the effect of improving the tan δ balance due to uneven distribution of the reinforcing filler tends to decrease, which is not preferable. In that case, the brittle point becomes high, and the curing phenomenon tends to occur at low temperatures, which is not preferable.

The type and combination of the rubber components (A) and (B) according to the present invention are not particularly limited, but the glass transition temperature (Tg _B ) of the rubber component ( _B ) is the rubber component (A).
Which is not higher than the glass transition temperature (Tg _A ) of Tg _B ≦
Tg _A ) is more preferable because it has a high effect of improving the tan δ balance due to uneven distribution of the reinforcing filler.

In the rubber composition for a tire tread according to the present invention, 30 to 80 parts by weight, preferably 30 to 65 parts by weight of at least one reinforcing filler selected from carbon black and silica is added to 100 parts by weight of the rubber component. By weight, the reinforcing filler concentration C _A in the rubber component (A) and the rubber component (B)
When the ratio of the reinforcing filler concentration C _B is 0 <C _A / C _B <1,
It is preferably unevenly distributed in the rubber component so that 0.1 ≦ C _A / C _B ≦ 0.3 (a difference in the concentration of the filler is created in the rubber composition). If the compounding amount of the filler is less than 30 parts by weight, abrasion resistance may be significantly reduced and the practical level may not be satisfied, which is not preferable, and if it exceeds 80 parts by weight, rolling resistance is increased, which is not preferable. Also C _A / C
_When the concentration ratio of _B is 1 or more, the balance of tan δ becomes poor, which is not preferable.

In the present invention, silica is used as a reinforcing filler.
It is preferable to add 0% by weight or more to 20 to 50% by weight.
In order to achieve the above-mentioned object, it is more preferable to mix them. Furthermore, it is preferable to add a silane coupling agent in an amount of 5 to 20% by weight based on the amount of silica. As the silane coupling agent, any one conventionally used in combination with silica can be used, and for example, bis- [3- (ethoxysilyl) -propyl] -tetrasulfide (trade name: S
i69, manufactured by Degussa) and the like.

The carbon used in the present invention has N ₂ SA of 65 to 160 m ² / g and a DBP oil absorption of 7
The silica has a water content of 10% or less, a BET of 100 to 300 m ² / g, and an oil absorption of 150 to 300 ml / 100 g.

The rubber composition according to the present invention has an end-modified S
Blended silica in the masterbatch containing SBR (A), by blending carbon black in the masterbatch containing the other diene rubber (B), wherein _{0 <C A / C B <} 1
It is preferable to have a difference in the concentration of. It should be noted that the rubber component (A) and the rubber component (B) may each contain either (a) carbon alone, (b) silica alone, or (c) any mixture of carbon and silica. There is no end.

The rubber composition for a tire tread of the present invention contains sulfur, in addition to the above-mentioned diene rubber and reinforcing filler.
Various additives commonly used for tires such as vulcanization accelerators, antioxidants, fillers, softeners, and plasticizers can be added, and such compounds are vulcanized by a general method. Tire treads can be manufactured. The amount of these additives may be a general amount.

[0017]

EXAMPLES The present invention will be further described below with reference to examples, but it goes without saying that the scope of the present invention is not limited to these examples.

Examples 1 to 14 Each component was blended according to the blending content (parts by weight) shown in Table I, and a silane coupling agent (Si69 manufactured by Degussa) was used.
3 parts, diethylene glycol 2 parts, zinc flower (Zanka No. 3 manufactured by Shodo Kagaku Co., Ltd.) 3 parts, stearic acid ("Lunac ya" manufactured by Kao Soap Co., Ltd.) 1 part, anti-aging agent (Sumitomo Chemical ( Antigen 6C (N-phenyl-)
N '-(1,3-dimethyl) -p-phenylenediamine)) 1.5 parts and wax (Sannoc manufactured by Ouchi Shinko Kagaku Co., Ltd.) 0.5 part (all are parts by weight), and a vulcanization accelerator. After mixing the compounding agent excluding sulfur with a 1.7-liter Banbury mixer for 5 minutes, a vulcanization accelerator (Nocceller NS-F (N-tert) manufactured by Ouchi Shinko Chemical Co., Ltd.) was added to the mixture.
-Butyl-2-benzothiazolyl-sulfenamide)) 1.7 parts by weight and 1.7 parts by weight of oil-treated sulfur were kneaded with an 8-inch test kneading roll machine for 4 minutes to obtain a rubber composition. These rubber compositions were press-vulcanized at 160 ° C. for 20 minutes to prepare target test samples, various tests were conducted, and the physical properties were measured. The physical properties of the obtained vulcanizate are shown in Table I.

[0019]

[Table 1]

The test method used in the above test is as follows.

1. tan δ Dynamic viscoelasticity (Rheograph manufactured by Toyo Seiki Seisakusho)
A value obtained by measurement under a predetermined condition of 60 ° C. In general, tan δ at 0 ° C. represents braking performance on a wet road surface, and tan δ at 60 ° C. represents rolling resistance. The larger tan δ (0 ° C.), the better the wet braking property, and tan δ (60
The lower the temperature (° C), the lower the rolling resistance.

2. Embrittlement point (° C) A low temperature impact embrittlement test was carried out in accordance with JIS K6301.

3. High temperature elongation (%) (100 ° C.) The elongation at break at 100 ° C. was measured according to JIS K6301 and this value was used as the resistance value of the mold chip.

[0024]

According to the present invention, as is clear from the results of Table I, the wet skid resistance is increased, the rolling resistance is reduced, and the low temperature embrittlement is improved without impairing the high temperature elongation. It is possible to provide a rubber composition for a tire tread suitable for use in the production of a prepared tire.

Examples 1, 3, 5, 7 and 9 are examples in which the filler is not unevenly distributed in the rubber component as in the conventional example.
(Examples), 4, 6, 8 and 10 are obtained by unevenly distributing fillers in the same manner with the same composition as in the above examples. Examples 1 and 2 are reference systems, and Example 2 (Example) has various physical properties well-balanced due to uneven distribution. In Examples 3 and 4, the terminal-modified SBR was changed to a low Tg type, and tan-δ balance was improved due to uneven distribution (tan-δ (0
C)) and reduction of tan-δ (60 ° C) at the same time) are not observed. In Example 6, carbon was unevenly distributed in 65% of the same polymer and silica was unevenly distributed in the remaining 35%.
This system is not suitable as a cap tread because it has a high embrittlement point regardless of the presence or absence of uneven distribution and a hardening phenomenon or the like is expected to occur at a low temperature because of BR alone. Examples 7 and 8 are intended to lower the Tg in the blend ratio of the polymer without changing the end-modified SBR to the low Tg type, but Examples 3 and 4
Similarly to the system of No. 1, no improvement in tan-δ balance is observed. In Examples 9 and 10, both tan-δ balance and high temperature elongation are not improved due to uneven distribution.

In Example 11 (Example), the mode of uneven distribution was changed based on Example 2. The combination of the terminal-modified SBR + SiO ₂ was more effective in improving the balance of physical properties than the combination of the terminal-modified SBR + CB. Is shown. Example 1
Nos. 2, 13 (Examples) and 14 are obtained by changing the filler concentration ratio based on the blend of Example 2, while Example 12 is one in which all the fillers are blended with NR and the effect of improving tan-δ balance is obtained. Is the best, but the elongation at break at high temperature is low and the moldability is poor, so that it is not suitable (filler concentration ratio is 0). Example 13
The SBR was mixed with 10 parts by weight of carbon, and the NR was mixed with 20 parts by weight of the remaining carbon and 30 parts by weight of silica, for a total of 50 parts by weight. As a result, the filler concentration ratio was 0.226, and at such a filler concentration ratio, each physical property balance (tan-δ balance, embrittlement point, high temperature elongation) was the highest.
Is good. In Example 14, 10 parts by weight of carbon was blended with NR, and 20 parts by weight of the remaining carbon and 30 parts by weight of silica were blended with SBR in a total of 50 parts by weight. as a result,
The filler concentration ratio is 1.956. 6 in this case
It is not preferable because the tan-δ at 0 ° C. increases and the rolling resistance performance may increase.

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Claims (4)

[Claims] 1. (i) (A) Terminal-modified solution-polymerized styrene
Butadiene copolymer rubber (SBR) and (B) said SB
To 100 parts by weight of a rubber component containing a diene rubber other than R, 30 to 80 parts by weight of (ii) at least one reinforcing filler selected from carbon black and silica is added to the concentration of the reinforcing filler in the rubber component (A). _A rubber composition for a tire tread, which is unevenly distributed in a rubber component such that the ratio of C _{A to} the reinforcing filler concentration C _{B in} the rubber component (B) is 0 <C _A / C _B <1. 2. The rubber composition according to claim 1, wherein the compounding ratio of the rubber component (A) and the rubber component (B) is 75 to 55:25 to 45 (weight ratio). 3. The rubber composition according to claim 1, wherein 10% by weight or more of the reinforcing filler is silica. 4. The reinforcing filler concentration ratio is 0.1 ≦ C _A / C.
The rubber composition according to claim 1, wherein _B ≦ 0.3.