JPH0748476A - Rubber composition for tire tread - Google Patents

Abstract

PURPOSE:To obtain the composition capable of lowering rolling resistance of tire and improving wet grip performance and abrasion resistance by blending a rubber component with a silica, a specific carbon black and a silane coupling agent. CONSTITUTION:This composition is obtained by blending (A) 100 pts.wt. of a rubber component containing (i) 10-90wt.% of natural rubber and/or a polyisoprene rubber and (ii) 90-10wt.% of styrene/butadiene copolymer having 10-50% styrene content and <=70mol% of vinyl component with (B) 20-60 pts.wt. of a silica (preferably having >=80wt.% purity and 50-300m<2>/g specific surface area for absorbing nitrogen) and (C) 10-50 pts.wt. of carbon black having 80-139m<2>/g specific surface area for absorbing nitrogen, >=140ml/100g DBP oil absorption amount and >=115ml/100g 24M4DBP oil absorption amount (with the proviso that the weight ratio of the component C/the component B is <=0.85) and (D) 1-10 pts.wt. of silane coupling agent. Furthermore, after these components A, B and D are blended, the component C is preferably blended with the blend.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a tire tread, and more specifically, rolling (or rolling) of a tire.
The present invention relates to a rubber composition for a tire tread that lowers resistance and improves wet grip performance (wet braking performance) and abrasion resistance.

[0002]

2. Description of the Related Art In the rubber industry, particularly in the tire industry, in order to reduce the rolling resistance of the tire to reduce the fuel consumption of the automobile and to improve the tire performance in accordance with the demand of the age of energy saving and resource saving, the wet performance is improved. There is a demand to improve wear resistance while maintaining grip performance.

A rubber composition containing silica (silicate type filler) is disclosed in Japanese Patent Application Laid-Open No. 61-218404, S.
Radial tires for passenger cars having a flatness of 50 to 65% and improved wear resistance, which are obtained by blending BR alone or a blend of SBR and natural rubber with a mixture of silica alone or a mixture of silica and carbon black are described. However, there is no mention of any reduction in rolling resistance of tires.

Japanese Patent Laid-Open No. 3-239737 discloses SBR.
Disclosed is a pneumatic tire in which a silica filler and carbon black are blended alone or in a blend thereof, and which can simultaneously satisfy wet skid properties, rolling resistance and abrasion resistance. However, since the pneumatic tire disclosed herein uses SBR containing less styrene single chain, there is a problem that wet skid property at low temperature is deteriorated. Further, there are few such SBRs on the market, and it is important to use a more general-purpose polymer in view of cost.

Japanese Patent Laid-Open No. 3-252431 discloses a BR
Alternatively, a pneumatic tire using a rubber composition in which a silica filler, carbon black, and a silane coupling agent are mixed in a rubber mainly composed of SBR in a tread and having satisfactory wet skid properties, rolling resistance, and abrasion resistance is disclosed. Has been done. However, this pneumatic tire also has a problem in that it uses SBR with less styrene single chain as in the above case.

Further, in Japanese Patent Laid-Open No. 5-51485,
Disclosed is a pneumatic tire in which a rubber composition containing carbon black and silica is used for a tread with respect to a diene rubber, without impairing initial wear resistance, steering stability, etc., and having improved oil content swelling resistance. Has been done. However, this publication makes no mention of reducing rolling resistance of tires.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention reduces the rolling resistance of tires to reduce the fuel consumption of automobiles and to improve wet grip performance and abrasion resistance based on the above-mentioned demand for energy saving. An object is to provide a composition for use.

[0008]

According to the present invention, (i)
(a) Natural rubber and / or polyisoprene rubber 10-9
0% by weight and (b) 100 parts by weight of a rubber component containing 90 to 10% by weight of a styrene-butadiene copolymer rubber having a styrene content of 10 to 50% by weight and a vinyl content of 70 mol% or less, and (ii) silica 20 to 60 parts by weight, (iii) nitrogen adsorption specific surface area (N ₂ SA) 80 to 139 m ² / g, DBP oil absorption amount 140 ml / 100 g or more and 24M4 DBP oil absorption amount 115 ml / 100 g or more carbon black 10 to 50
Parts by weight (however, carbon black (iii) / silica (ii)
(A weight ratio of 0.85 or less) and (iv) a silane coupling agent in an amount of 1 to 10 parts by weight.

The structure of the present invention will be described in more detail below. As described above, the rubber component blended in the rubber composition of the present invention is (a) natural rubber (NR) and / or polyisoprene rubber (IR) 10 to 90% by weight, preferably 20 to
Styrene-butadiene copolymer rubber (SBR) 90 to 10 with 80 wt% and (b) styrene content of 10 to 50 wt%, preferably 10 to 40 wt% and vinyl content of 70 mol% or less, preferably 60 mol% or less. % By weight, preferably 8
It is a blend with 0 to 20% by weight. Since this system has a vinyl content of SBR of 70 mol% or less, the incompatible system (t
The temperature dispersion of an δ is 2 peaks). The NR, IR and SBR used in the present invention may be any conventionally used in tire tread blending (provided that the styrene content and vinyl content of SBR are as described above). .

In the compounding of the rubber component of the rubber composition for a tire tread according to the present invention, the vinyl content of SBR is 70.
When it exceeds mol%, the temperature dispersion curve of tan δ when blended with NR has one broad peak, and the balance between good wet grip performance and low rolling resistance is lost, which is not preferable. Further, if the styrene content of SBR is less than 10% by weight, wet grip performance is deteriorated, and if it exceeds 50% by weight, rolling resistance increases, which is not preferable. Further, if the blending amount of NR (or IR) is less than 10% by weight, the tensile strength and the like will decrease, which is not preferable, and the blending amount of SBR is 10%.
If it is less than weight%, the wet grip performance is deteriorated, which is not preferable.

In the rubber component of the rubber composition for tread according to the present invention, in addition to NR and / or IR which is the first component and SBR which is the second component, NR (and / or) as the third component.
Or IR) / SBR system in an amount that maintains 100 parts by weight of these rubber parts to 30 parts by weight or less of the third part within a range that maintains the incompatible state.
It can be replaced by a rubber component. As such a third rubber component, for example, another S outside the range of the above (b)
Examples thereof include BR, polybutadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), ethylene / propylene / non-conjugated diene terpolymer rubber (EPDM), and chloroprene rubber (CR).

The rubber composition for a tread according to the present invention contains 20 to 60 parts by weight, preferably 25 to 50 parts by weight of silica based on 100 parts by weight of the rubber component. As the silica used in the present invention, any silicate-based filler that has been generally used as a rubber compound for tire treads, such as dry process silica and wet process silica, can be used, and the silica purity is preferably 80. A material having a nitrogen adsorption specific surface area (BET method) of 50 to 300 m ² / g in an amount of not less than wt% is used. If the amount of silica is less than 20 parts by weight, the reinforcing property is insufficient (only 17 parts by weight of carbon black can be added), and if it exceeds 60 parts by weight, heat generation during mixing increases and the risk of "burning" increases. Moreover, there is a problem that the workability becomes poor due to the excessively high viscosity, which is not preferable.

The tread rubber composition according to the present invention comprises:
As described above, the nitrogen adsorption specific surface area (BET method) (N ₂ S
A) 80 to 139 m ² / g, DBP oil absorption (measured by method A [mechanical method]) 140 ml / 100 g or more, and 24 M
4DBP oil absorption 115ml / 100g or more, preferably 1
20 ~ 200ml / 100g carbon black rubber 1
10 to 50 parts by weight, preferably 15 to 4 per 100 parts by weight
Add 0 parts by weight. The carbon black / silica (weight ratio) in the rubber composition of the present invention is 0.85 or less. If the blending amount of carbon black is less than 10 parts by weight, the reinforcing property will be insufficient, which is not preferable. On the contrary, if it exceeds 50 parts by weight, heat generation during mixing increases and the risk of "burning" increases and the viscosity increases. As a result, the processability becomes extremely poor (it is necessary to mix silica in an amount of 58.8 parts by weight or more), which is not preferable. When the carbon black / silica (weight ratio) exceeds 0.85, it is considered that the reaction between silica and the rubber polymer via the coupling agent is hindered, and the rolling resistance cannot be lowered, which is not preferable.

If the N ₂ SA of the carbon black compounded in the rubber composition of the present invention is less than 80 m ² / g, the abrasion resistance is insufficient, and if it exceeds 139 m ² / g, dispersion during kneading is difficult, In addition, heat generation is increased and rolling resistance is further increased, which is not preferable. If the DBP of carbon black is less than 140 ml / 100 g and the carbon black / silica ratio is 0.85 or less, sufficient abrasion resistance cannot be obtained. 24M4DBP oil absorption is 115
If it is less than ml / 100 g, sufficient abrasion resistance cannot be obtained, which is not preferable.

The tread rubber composition according to the present invention comprises:
Further, as an essential component, a silane coupling agent 1 to 10 times
Parts (preferably 3 to 15% by weight of silica content)
To meet. Conventional silane coupling agents used in the present invention
Any silane coupling agent commonly used in
Can be used, and RSiX is a typical example. ₃
(R: organic functional group capable of binding to the rubber component, for example, glycid
Represents a xy group, a methacrylic group, or a vinyl group, and X is an alkoxy group.
The ones that have a chemical structure of
You can Required amount of silane coupling agent
Not only will there be no effect if more than the above, but also the cost will increase
It is not preferable.

The rubber composition for a tire tread of the present invention contains, in addition to the above-mentioned raw rubber component, silica, carbon black and a silane coupling agent, a compounding agent usually used in the rubber industry such as sulfur and a softening agent. If necessary, an antioxidant, a vulcanization accelerator, a filler, a plasticizer, etc. are appropriately compounded in the range of the usual compounding amount, and a tire tread can be vulcanized by a general method. . For example, the content of sulfur is preferably 1.2 parts by weight or more, more preferably 1.5 to 3.0 parts by weight, per 100 parts by weight of rubber. There is no particular limitation on the mixing order of the respective components for producing the tire tread composition of the present invention, but the rubber component and silica and the silane coupling agent are first mixed, and then the carbon black is mixed. Is preferable because the mixing and dispersing properties of the compound are improved.

[0017]

According to the present invention, first, by using an incompatible two-component system (or incompatible three-component system) of NR (and / or IR) / SBR as the rubber component, It contributes to the improvement, SBR contributes to the wet grip performance, and by making it incompatible, the temperature dispersion of tan δ becomes a sharp peak with 2 peaks, so tan
Since δ (60 ° C.) does not rise and tan δ (0 ° C.) also rises, it is effective in obtaining low rolling resistance and good wet skid property.

According to the present invention, since silica is blended as a reinforcing agent and the silica is selectively distributed to the NR side, S
The wear resistance can be improved without affecting the tan δ peak due to BR (that is, without increasing tan δ (60 ° C.)). On the other hand, in the present invention, since carbon black having a so-called high structure having the above-described characteristics is blended, the SBR of the rubber component is kept at a carbon black / silica weight ratio of 0.85 or less without lowering abrasion resistance. The side can be reinforced (carbon black has a high affinity with SBR). In the present invention, carbon black / silica (weight ratio) is set to 0.8.
By setting the ratio to 5 or less, it is possible to prevent the formation of bound rubber due to silica, suppress the increase in hardness, and solve the problem of poor riding comfort due to the increase in hardness due to the incorporation of silica.

[0019]

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 9 and Comparative Examples 1 to 13 Rubber compositions having the compounding contents (parts by weight) shown in Tables 1 to 3 were prepared by mixing and kneading with a Banbury mixer and a kneading roll machine according to a conventional method (Comparative Examples 1 to 13). And Examples 1-9).
These rubber compositions were press-vulcanized at 160 ° C. for 20 minutes to prepare target test pieces, various tests were conducted, and the physical properties thereof were measured. The results are shown in Tables 1 to 3. The test method is as follows.

Impact resilience (Lupke) The impact resilience was measured according to the method of JIS K6301 at 60 ° C. The larger the value at 60 ° C, the smaller the rolling resistance and the better.

Abrasion resistance (pico abrasion) Measured in accordance with ASTM D2228 method using a pico abrasion tester. (Abrasion amount of conventional example) × 100 / (Abrasion amount of sample) is expressed as an index. Therefore, the larger the value, the better the wear resistance.

Measured according to the method of JIS K6301 under the condition of JIS hardness 20 ° C.

Wet skid resistance index 23 ° C. using Stanley Portable Skid Tester
(Both sample temperature and water temperature) were measured using a safety walk made by 3M Co., Ltd. as the road surface, and shown as an index for the conventional example. The larger the value, the better the wet grip.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

Footnotes to Tables 1 to 3 * 1: Styrene content = 25% by weight, vinyl content 35% by mole * 2: Styrene content = 14% by weight, vinyl content 75% by mole * 3: Silica purity = 98%, nitrogen adsorption Specific surface area = 19
5 m ² / g * 4: Characteristics of carbon black used Nitrogen specific surface area DBP oil absorption 24M4 DBP species (m ² / g) (ml / 100g) (ml / 100g) No. 1 84 130 111 No. 295 133 111 No. 3 ^* 128 152 121 No. 4 ^* 121 181 132 No. 4 5 142 143 118 No. 6 ^* 138 163 130 No. 6 7 ^* 127 170 128 ──────────────────────────────── *: Carbon black within the scope of the present invention * 5: Bis -(3-Triethoxy-propyl) -tetrasulfide (Si69: manufactured by Degussa) * 6: diethylene glycol * 7: N- (1,3-dimethylbutyl) -N'-phenyl-P-phenylenediamine * 8: N- t-Butyl-2-benzothiazole sulfenamide

[0028]

INDUSTRIAL APPLICABILITY As described in detail above, the rubber composition for tire tread of the present invention is excellent in wet grip performance as seen in the values of the wet skid resistance index of each example, and also in each case. Example impact resilience (60
(° C), a vulcanizate having low rolling resistance and excellent abrasion resistance can be obtained.

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Claims (1)

[Claims] 1. A styrene-butadiene copolymer rubber having (i) (a) 10 to 90% by weight of natural rubber and / or polyisoprene rubber, and (b) 10 to 50% by weight of styrene content and 70 mol% or less of vinyl content. (Ii) 20 to 60 parts by weight of silica, (iii) 80 to 139 m ² / g of nitrogen adsorption specific surface area, and D to 100 parts by weight of a rubber component containing 90 to 10% by weight.
BP oil absorption 140ml / 100g or more and 24M4DBP
Carbon black with oil absorption of 115 ml / 100 g or more
To 50 parts by weight (however, a carbon black (iii) / silica (ii) weight ratio of 0.85 or less) and (iv) a silane coupling agent (1 to 10 parts by weight).