JPH08127672A - Tread rubber composition for tire - Google Patents

Abstract

PURPOSE: To obtain a tread rubber composition for high-performance tires highly excellent in wear resistance and blowout resistance while retaining their high grip-performance. CONSTITUTION: This tread rubber composition for tires contains (A) 100 pts.wt. of a polymer blend with an average styrene content of 25 to 45wt.%, consisting of 20 to 60 pts.wt. of at least one kind of styrene-butadiene copolymer rubber (Tg : >-25 deg.C) and the balance of at least one kind of diene-rubber (Tg:<=-30 deg.C), (B) 60 to 130 pts.wt. of carbon black (CTAB: 130 to 180m<2> /g, 24M4DBP: 106 to 135ml/100g and ΔDst/Dst: 0.60 to 0.80) and (C) 5 to 30 pts.wt. of an ester-based plasticizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tread rubber composition for tires, and more particularly to a tread rubber composition for high performance tires having improved tire wear resistance and blowout resistance while maintaining high grip performance. Regarding

[0002]

2. Description of the Related Art In order to obtain high exercise performance of a high performance tire, it is necessary to use a tread rubber composition for a tire having a high grip performance (both wet and dry). In order to improve the grip performance of the tread rubber composition for tires, for example, a polymer having a high glass transition temperature is used as a rubber component (JP-A-61-87).
No. 737, JP-A-1-17523), blending a large amount of a softening agent and carbon black, and using carbon black having a small particle size.

[0003]

However, although these tread rubber compositions for tires show high grip performance, there is a problem that abrasion resistance and blowout resistance are significantly reduced. To solve this problem, the present inventors have previously proposed that it is possible to balance the grip and the wear resistance at a high level by using a specific carbon (JP-A-6-93136). .
However, even with such a composition, the wear resistance and blow resistance, which are important properties of the tire, are still insufficient.

Accordingly, it is an object of the present invention to provide a tread rubber composition for a high performance tire which has extremely good wear resistance and blowout resistance while maintaining high grip performance.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that by using a specific polymer, carbon black and a plasticizer,
It has been found that it is possible to achieve both grip performance, wear resistance and blowout resistance.

That is, according to the present invention, (i) 20 to 60 parts by weight of at least one styrene-butadiene copolymer rubber having a glass transition temperature (Tg) higher than -25 ° C. and the balance glass transition temperature (Tg). ) Is composed of at least one diene rubber having a temperature of -30 ° C. or less, and has an average styrene content of 2
100 parts by weight of polymer of 5 to 45% by weight, (ii) CTA
B 130-180 m ² / g, 24M4DBP 106-
135 ml / 100 g and ΔDst / Dst 0.60
Provided is a tread rubber composition for a high performance tire, which comprises 60 to 130 parts by weight of 0.80 carbon black and 5 to 30 parts by weight of (iii) an ester plasticizer.

The structure of the present invention will be described in detail below. As described above, the polymer component (rubber component) of the tire tread rubber composition of the present invention has Tg of − as the first component.
Styrene higher than 25 ° C, preferably -20 ° C or higher-
The butadiene copolymer polymer (A) was added to the total polymer content of 10
20-60 parts by weight, preferably 30-5, relative to 0 parts by weight
Add 0 parts by weight. The blending amount of this polymer (A) is 20
If it is less than 60 parts by weight, high grip performance cannot be obtained when it is used as a tire, and if it exceeds 60 parts by weight, abrasion resistance remarkably decreases. The polymer (A) may be a single kind or a mixture of two or more kinds, and is generally a high styrene SBR having a high bound styrene amount and / or a high vinyl SB having a high vinyl binding amount.
R. The high vinyl SBR can be produced by a conventional method by a solution polymerization method using alkyllithium as a catalyst.

The polymer component of the tire tread rubber composition of the present invention has a second component, Tg, of -30 ° C or lower,
A diene rubber (polymer B) having a temperature of −35 ° C. or less, preferably a styrene-butadiene copolymer rubber (SBR) or a polybutadiene rubber is preferably added as the balance. As such a polymer B, SBR, BR or the like which has been conventionally used for tire compounding can be used. Particularly preferred is a random SBR in which the ratio of 8 or more styrene chains is 10% or less of the styrene content. Compared to random SBR, SBR containing block styrene is not preferable because it has reduced wear resistance. In the present invention, the glass transition point (Tg) is measured by using a differential thermal analyzer (DSC) manufactured by DuPont, and ASTM D341 is used.
Measured at a temperature rising rate of 10 ° C./min in accordance with 8-82, and the intersection of the tangent line of the inflection point of the glass transition and the extrapolation of the baseline is T
It was set to g.

As the polymer component of the tire tread rubber composition of the present invention, as described above, a mixture of the polymer (A) and the polymer (B) having a specific Tg is used.
The average styrene content in all polymers is 25-45% by weight,
It is preferably 30 to 35% by weight. When the average styrene content in the polymer is less than 25% by weight, it is not preferable because it has a low grip as a tread rubber for ultra-high performance tires. On the contrary, when it exceeds 45% by weight, blowout resistance and abrasion resistance are deteriorated, which is preferable. Absent.

As described above, the carbon black compounded in the tire tread rubber composition of the present invention is CTAB.
(Surface area m ² / unit weight of carbon black calculated from the amount of adsorbed cetyltrimethylammonium bromide
g) (measured according to the method of ASTM D3765-80) 130 to 180 m ² / g, preferably 135 to 170
m ² / g, 24M4DBP (measured according to the method of ASTM D3493) 106-135 ml / 100 g, preferably 110-125 ml / 100 g, ΔDst / Dst
It is necessary to satisfy the requirement of 0.60 to 0.80, preferably 0.65 to 0.75, and in the present invention, 60 to 130 parts by weight, preferably 70 to 120 parts by weight of such carbon black is added to 100 parts by weight of the polymer content. Add parts by weight.

The carbon black compounded in the tire tread rubber composition of the present invention has a CTAB of 130-1.
It should be 80 m ² / g. The value of CTAB is 130
If it is smaller than m ² / g, both the grip performance (tan δ) and the wear resistance of the obtained vulcanized rubber are deteriorated, which is not preferable. Conversely, if CTAB is larger than 180 m ² / g,
It becomes difficult to disperse carbon black in the polymer, and heat generation becomes high, which is not preferable. Also,
24M4DBP of carbon black used in the present invention is 1
It should be 06-135ml / 100g, and if this value is smaller than 106ml / 100g, sufficient abrasion resistance cannot be obtained, and conversely, the value of 24M4DBP is 135ml / 100g.
If it is larger, the production of carbon black is difficult, and the hardness of the obtained rubber composition is too high, which leads to deterioration in grip performance when used as a tire, which is not preferable.

Further, the carbon black used in the present invention must have a ΔDst / Dst of 0.60 to 0.80. When the value of ΔDst / Dst is smaller than 0.60, the grip performance is high, but the heat generation is high and the production of carbon black itself becomes difficult. On the other hand, when ΔDst / Dst is larger than 0.80, grip performance tends to deteriorate and abrasion resistance tends to deteriorate, which is not preferable. Therefore, ΔDst / Ds
The range of t of 0.60 to 0.80 is the optimum range for balancing wear resistance and grip performance.

In the tire tread rubber composition according to the present invention, 60 to 130 parts by weight of the above carbon black should be blended with 100 parts by weight of the polymer content.
If the blending amount of carbon black is less than 60 parts by weight, the grip performance is deteriorated, which is not preferable. On the contrary, if it exceeds 130 parts by weight, there is a problem in workability such as dispersing carbon black, and abrasion resistance and Blowout resistance is also reduced, which is not preferable.

It is important to add an ester plasticizer as a softening agent to the tread rubber composition for tires of the present invention. By blending an ester plasticizer,
Wear resistance and blowout resistance are unexpectedly improved. The present inventors presume that the microscopic dispersion of carbon black was improved. The compounding amount of the ester plasticizer is 5 to 30 parts by weight based on 100 parts by weight of the polymer content,
It is preferably 8 to 20 parts by weight. If the compounding amount of the ester plasticizer is less than 5 parts by weight, the effect of improving the abrasion resistance is small, which is not preferable. It is not preferable. When an ester plasticizer having a kinematic viscosity (25 ° C.) of 100 cSt or more is used, the grip property and the wear resistance are particularly excellent in balance.

Examples of the ester plasticizer used in the present invention include general phthalic acid ester, adipic acid ester, sebacic acid ester, glycerin ester, maleic acid ester, fumaric acid ester, pyromellitic acid ester and the like. . Especially, the kinematic viscosity (25 ℃) is 1
Preferred examples of 00 cSt or more include dipentaerythritol ester, pentaerythritol ester, trimethylolpropane ester, trimethylolethane ester and the like.

In the tread rubber composition for tires of the present invention, in addition to the polymer content and carbon black, sulfur,
Various additives that are commonly used for tires, such as vulcanization accelerators, antioxidants, fillers, and softeners, can be added, and such a mixture is vulcanized by a general method to form a tire tread. It can be manufactured. The compounding amount of these additives may be a general amount. For example, the content of sulfur is preferably 1.0 part by weight or more, more preferably 1.5 to 3.0 parts by weight, per 100 parts by weight.

[0017]

The present invention will be described in more detail below with reference to Examples and Comparative Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples.

Examples 1 to 4 and Comparative Examples 1 to 12 The respective components were blended according to the blending content (parts by weight) shown in Table 1, and the vulcanization accelerator and the raw material rubber excluding sulfur and the blending agent were 1.7. After mixing for 5 minutes with a liter Banbury mixer, a vulcanization accelerator and sulfur were kneaded for 4 minutes with an 8-inch test kneading roll machine to obtain a rubber composition. These rubber compositions were press-vulcanized at 160 ° C. for 25 minutes to prepare target test pieces, various tests were conducted, and their physical properties were measured. The physical properties of the obtained vulcanizate are also shown in Table 1. In addition, polymer, carbon black characteristics,
The physical properties of vulcanized products were measured by the following methods.

Test Method (Physical Properties of Carbon Black) 1. CTAB: Complies with ASTM D3756 2.24M4DBP: Complies with ASTM D3493 3. ΔDst, Dst: A dry carbon black sample was mixed with a 20% by volume aqueous ethanol solution containing a small amount of a surfactant to prepare a dispersion having a carbon black concentration of 5 mg / 100 cc, which was sufficiently dispersed by ultrasonic waves to form a sample. To do. Disc centrifuge device (UK JoiceLoebl
(Manufactured by the company) is set at a rotation speed of 8000 rpm, 10 mL of spin solution (distilled water) is added, and then 0.5 mL of buffer solution (aqueous ethanol solution) is injected. Then, the sample solution 0.
5 mL is added with a syringe to start centrifugal sedimentation, and at the same time, a recorder is operated to optically create a distribution curve of aggregate Stokes equivalent diameter. The Stokes' equivalent diameter at the maximum frequency in the obtained distribution curve is defined as Dst (nm). The half-width (ΔDst) is the aggregate distribution value at 1/2 of the most frequent frequency.

(Physical Properties of Vulcanized Material) 1. tanδ Using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho, 0 under the condition of strain rate of 10 ± 2% and frequency of 20Hz by extensional deformation.
Measured in ° C. The tan δ at 0 ° C. corresponds to the wet grip value, and the higher this value, the better the wet performance.

2. Dry and Wet Skid Using a British Portable Skid Tester, measurement was performed under conditions of a dry road surface and a wet road surface and a temperature of 20 ° C., and Comparative Example 1 was set to 100 and indicated as an index. The higher the value, the better the skid resistance.

3. Lambourn abrasion The Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) was used to measure the abrasion loss under a predetermined condition of a temperature of 20 ° C., and Comparative Example 1 was set to 100 and indicated as an index. The larger the value, the better the wear resistance.

4. Blowout resistance Blowout resistance is a load of 15 kg and a stroke of 5.71.
mm, the frequency is 1800 rpm, and the time until blowout occurs in an atmosphere of 100 ° C. is measured.
It is displayed as an index when 00 is set. The larger the value, the better the blowout resistance.

(Polymer physical properties) The amount of styrene was measured by an Hampton spectrophotometer described in Anal. Chem., 21. 923 (1949) using an infrared spectrophotometer.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

Table 1 Footnote (For oil-oil products, only the rubber content is shown as a compounding ratio, and the oil is added to the aromatic oil.) * 1: Nipol 9520 (manufactured by Nippon Zeon Co., Ltd., styrene content =) 35%, Tg = -33 ° C) * 2: Nipol 1502 (manufactured by Nippon Zeon Co., Ltd., styrene amount = 23.5%, Tg = -52 ° C) * 3: Prototype SBR (prototype E-SBR, St = 45) %, T
g = -21 ° C.) * 4: The characteristics of carbon black are as follows. ────────────────────────────────── Prototype 1 Prototype 2 Prototype 3 Prototype 4 was resistance N110 ( CB1) (CB2) (CB3) (CB4) CTAB 122 134 151 151 140 156 24M4DBP 99 98 113 113 110 116 ΔDst 73 39 39 78 45 46 Dst 82 64 64 93 66 66 ΔDst / Dst 0.89 0.61 0.84 0.68 0.71 ────────────────────────────────── * 5: Diamond Black A (manufactured by Mitsubishi Kasei Co., Ltd.) ) * 6: Including oil in polymer. * 7: Dioctyl sebacate (DOS), kinematic viscosity (25
℃) = 19.1 cSt * 8: Dipentaerythritol ester, kinematic viscosity (25
℃) = 375.9 cSt * 9: Zinc flower ... “Zinc flower No. 3” manufactured by Shodo Kagaku Co., Ltd. * 10: Stearic acid ... “Lunac manufactured by Kao Soap Co., Ltd.
YA "* 11: Antiaging agent ... N-phenyl-N '-(1,3-
Dimethyl) -p-phenylenediamine ("Antigen 6C" manufactured by Sumitomo Chemical Co., Ltd.) * 12: Sulfur ... Oil-treated sulfur * 13: Vulcanization accelerator ... N-tert-butyl-2-benzothiazolyl-sulfenamide ( Ouchi Shinko Chemical Co., Ltd.
"Nox Cellar NS-F")

[0029]

As is clear from the results of Table 1, Comparative Examples 1 to 6 are examples using compositions outside the scope of the present invention in terms of carbon black properties or ester plasticizer blending. . In addition, Comparative Examples 7 to 9 have the same polymer characteristics as Comparative Example 1
0 to 11 are examples in which the amount of carbon black is blended, and Comparative Example 12 is an amount in which the amount of ester plasticizer is blended is outside the range of the present invention. In comparison with these, Examples 1 to 4 according to the present invention,
Clearly, it has a good balance of wear resistance, grip characteristics and blowout resistance.

Claims (2)

[Claims] 1. (i) Glass transition temperature (Tg) is -25.
20 to 60 parts by weight of at least one styrene-butadiene copolymer rubber having a glass transition temperature (Tg) of -30 ° C. or less and an average styrene content of 25 to 45. (Ii) CTAB 130-180 m ² / g, 24M4DB, relative to 100 parts by weight of the polymer.
P 106-135 ml / 100 g and ΔDst / Dst
0.60 to 0.80 carbon black 60 to 130
A tread rubber composition for a tire, which comprises 5 parts by weight and (iii) 5 to 30 parts by weight of an ester plasticizer. 2. The tread rubber composition for a tire according to claim 1, wherein the ester plasticizer has a kinematic viscosity (25 ° C.) of 100 cSt or more.