JP2005344063A - Tire tread rubber composition for high load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire tread rubber composition for high load which highly enhances abrasion resistance without exerting bad influences on heat build-up properties and other properties. <P>SOLUTION: The tire tread rubber composition comprises 100 pts.wt. of a diene rubber and, incorporated therewith, 40-60 pts.wt. of carbon black having a CTAB adsorption specific surface area of at least 120 m<SP>2</SP>/g, a compressed DBP oil absorption of at least 90 ml/100 g and containing pores having a pore size of 25-30 nm which account for at least 30 ml/100 g in the pore volume in aggregates. A strong network structure is formed by accelerating bonding between carbon black and the rubber component polymer by increasing the volume of pores having a pore size within a specified range in pores among carbon black aggregates. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition excellent in wear resistance used as a rubber composition for forming a tread portion in a heavy duty tire used for a large vehicle such as a truck or a bus.

  In heavy duty tires used for trucks and buses, the wear resistance of the tread portion is extremely important. Conventionally, in order to improve the wear resistance, a high cis type having a high cis-1,4 content is used for the butadiene rubber used as the rubber component, or a small particle size is used for the carbon black as the filler. Measures have been proposed (for example, Patent Documents 1 to 3 listed below), such as using a material having a high structure, using a material having a high structure, improving surface activity, and increasing the amount added.

Patent Document 4 below defines the relationship between N ₂ SA, DBP and IA (iodine adsorption amount) of carbon black, and also defines the relationship between TINT (specific coloring amount) and Dst (Stokes equivalent diameter). By doing so, a tread rubber composition has been proposed that is excellent in wear resistance and fuel efficiency and does not deteriorate the workability during production.

Further, in Patent Document 5 described below, it is used for a tire for a passenger car, not a heavy duty tire. In a rubber composition for a tire tread, N ₂ SA is 75 to 125 m ² / g, and the compressed DBP oil absorption is It belongs to a hard system region of 100 to 130 ml / 100 g and defines the relationship between the half-value width ΔDst and Dst (Stokes mode diameter), and the relationship between the mode diameter Dp of the pore diameter distribution of the aggregate and its half-value width ΔDp. It has been proposed to use a defined carbon black.
Japanese Patent Laid-Open No. 11-60984 Japanese Patent Laid-Open No. 11-60985 JP 2000-80302 A Japanese Patent Laid-Open No. 2001-2835 JP-A-7-179672

  Although the above-mentioned conventional measures can surely improve the wear resistance, they cannot satisfy the recent requirement for high wear resistance, and the heat generation necessary for the tread rubber of heavy duty tires There was also a drawback that it adversely affected properties such as cut resistance / chip resistance.

  The present invention has been made in view of the above points, and provides a heavy-load tire tread rubber composition capable of highly improving wear resistance without adversely affecting characteristics such as heat generation. With the goal.

  The present inventor pays attention to the pores between the aggregates of carbon black, and increases the pore volume of the pores having a predetermined range, thereby forming a strong network structure by promoting the bonding between the carbon black and the rubber component polymer. Thus, the present inventors have found that the wear resistance can be improved to a high degree without adversely affecting the properties such as exothermic properties, and have completed the present invention.

That is, the tire tread rubber composition for heavy loads according to the present invention has a CTAB adsorption specific surface area of 120 m ² / g or more, a compressed DBP oil absorption of 90 ml / 100 g or more with respect to 100 parts by weight of the diene rubber, and 40-60 parts by weight of carbon black in which the pore volume of 25-30 nm occupies 30 ml / 100 g or more in the inter-aggregate pore volume is contained.

  In the rubber composition of the present invention, the diene rubber may be composed of 100 to 50% by weight of natural rubber and / or isoprene rubber and 0 to 50% by weight of butadiene rubber.

  According to the present invention, by using the specific carbon black described above, the network between the carbon black and the polymer of the rubber component can be further strengthened, and therefore, the wear resistance is highly enhanced without impairing heat generation. Can be improved.

  Hereinafter, matters relating to the implementation of the present invention will be described in detail.

  In the rubber composition of the present invention, examples of the diene rubber used as the rubber component include natural rubber, and diene synthetic rubbers such as isoprene rubber, butadiene rubber, and styrene-butadiene rubber. It may be used alone or in combination of two or more.

  Preferably, the diene rubber is composed of 100 to 50% by weight of natural rubber and / or isoprene rubber and 0 to 50% by weight of butadiene rubber. That is, natural rubber and / or isoprene rubber alone or a blend of this with butadiene rubber is preferable. When blended, the natural rubber and / or isoprene rubber is preferably 50% by weight or more and the butadiene rubber is preferably 50% by weight or less, more preferably, the natural rubber and / or isoprene rubber is 50 to 90% by weight, The butadiene rubber is 10 to 50% by weight.

  As the butadiene rubber, a high cis type rubber having a cis-1,4 bond content of 95% or more is preferable for improving wear resistance. Here, the cis-1,4 bond content is a value measured by an infrared absorption spectrum method (Morello method).

  The carbon black used in the rubber composition of the present invention satisfies the following (1) to (3).

(1) CTAB adsorption specific surface area is 120 m ² / g or more,
(2) The compressed DBP oil absorption is 90 ml / 100 g or more,
(3) The amount occupied by the pore diameter of 25-30 nm in the pore volume between aggregates is 30 ml / 100 g or more.

The CTAB (cetyltrimethylammonium bromide) adsorption specific surface area (hereinafter sometimes simply referred to as “CTAB”) in (1) above is a value measured according to ASTM D3765, and is the particle diameter of carbon black. It is an indicator. In the present invention, a CTAB having a small particle size of 120 m ² / g or more is used, and if it is less than 120 m ² / g, good wear resistance cannot be obtained as a tread rubber of a heavy duty tire. The upper limit of CTAB is not particularly limited, but is preferably 180 m ² / g or less in order to ensure the processability of the tread rubber. More preferably, it is 130 m ² / g or less. The compressed DBP (dibutyl phthalate) oil absorption amount in (2) above is the 24M4 DBP oil absorption amount (hereinafter sometimes simply referred to as “24M4DBP”), and is ASTM D3493. And is an index of the structure of carbon black. In the present invention, a high structure product in which 24M4DBP is 90 ml / 100 g or more is used, and if it is less than 90 ml / 100 g, good wear resistance cannot be obtained as a tread rubber of a heavy duty tire. The upper limit of 24M4DBP is not particularly limited, but is preferably 150 ml / 100 g or less. More preferably, it is 130 ml / 100 g or less.

  The pore volume between aggregates in (3) above is the volume of pores that are voids and pores between aggregate particles in the structure of aggregates that are aggregates of carbon black particles. The present invention is characterized in that, among the pore volumes, carbon black having a pore diameter of 25 to 30 nm and a volume of 30 ml / 100 g or more is used.

  In general, the chain end distance (distance between both ends) of the polymer constituting the rubber component is about 15 to 20 nm. Therefore, in carbon black, the polymer volume can be increased by increasing the pore volume having the same pore size. And the carbon black network (network structure) can be strengthened. This can also prevent rubber molecules from slipping when the rubber is deformed, and can suppress heat generation. In the past, attempts have been made to sharpen the pore size distribution between aggregates in order to improve the wear resistance, but what actually contributes to the improvement of the wear resistance is the pore diameter of 25 to 30 nm. However, by setting the volume of the pore having this range of pores to a predetermined value or more, the wear resistance can be improved to a high degree, and this is the greatest feature of the present invention.

  In addition, when there is much pore volume whose pore diameter is less than 25 nm, since a polymer molecule will be distorted if polymer molecule enters there, a favorable physical property cannot be obtained. In addition, when the pore volume having a pore diameter exceeding 30 nm is large, the aggregate strength becomes weak and the aggregate is destroyed at the time of mixing, so that good physical properties cannot be obtained.

  The upper limit of the amount occupied by the pore diameter of 25 to 30 nm is not particularly limited, and it can be said that the larger this value is, the better the wear resistance is. However, the upper limit is usually about 50 ml / 100 g.

Here, the pore volume between aggregates is measured by a mercury intrusion method, and more specifically, a particle size of 0.25 to 0.25 in a dedicated cell of a mercury porosimeter (“Pore Sizer 9300” manufactured by Micromeritics). A carbon black pellet adjusted to 0.50 mm is loaded, and mercury is injected in a pressure range of 25 to 2000 lb / in ² to measure the pressure at the point where the amount of mercury intrusion increases rapidly, and the pore volume is calculated from this value. To do. More specifically, since the data obtained from the above values are cumulative voids, the pore volume is calculated by calculating the area in the pore diameter range of 25 to 30 nm after conversion to the intergranular void distribution curve by differential calculation. .

In the carbon black used in the present invention, the nitrogen adsorption specific surface area (N ₂ SA) is not particularly limited, but is preferably about 120 to 180 m ² / g. Here, N ₂ SA is a value measured according to ASTM D3037.

  The compounding amount of the carbon black is 40 to 60 parts by weight with respect to 100 parts by weight of the rubber component. When the blending amount of the carbon black is less than 40 parts by weight, the wear resistance deteriorates, and when it exceeds 60 parts by weight, the exothermic property deteriorates.

  In addition to the components described above, the rubber composition of the present invention is generally used in a tread rubber composition for heavy duty tires such as anti-aging agent, zinc white, stearic acid, softening agent, vulcanizing agent, and vulcanization accelerator. Various additives can be blended.

  The heavy load tire tread rubber composition of the present invention comprising the above is used as a rubber composition for a tread portion of a heavy load pneumatic radial tire such as a truck or a bus, and is vulcanized and molded by a conventional method. A tread portion can be formed. When the tread portion is made of this rubber composition, wear resistance can be improved to a high degree without adversely affecting properties such as heat generation by using the specific carbon black described above.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Table 1 below shows 100 parts by weight of a rubber component in which 20 parts by weight of butadiene rubber (“BR01” manufactured by JSR (cis-1,4 bond content = 96%)) is blended with 80 parts by weight of natural rubber (RSS 3). 50 parts by weight of carbon black having characteristic values are blended, and as other components, 3 parts by weight of zinc white (Mitsui Kinzoku “Zinc Hana 1”), 3 parts by weight of stearic acid (manufactured by Nippon Oil & Fats), anti-aging 1 part by weight of the agent (“6PPD” manufactured by Monsanto), 2 parts by weight of sulfur (manufactured by Shikoku Kasei) and 1 part by weight of the vulcanization accelerator (“TBBS” manufactured by Sanshin Chemical) are added and kneaded with a Banbury mixer. A heavy tire tread rubber composition was prepared.

  The carbon black is a multi-stage narrow chamber having a combustion chamber having a tangential air supply port at the furnace head and a combustion burner mounted in the furnace axis direction, and a feed oil injection nozzle coaxially connected to the combustion chamber. It was obtained by adjusting the conditions for split introduction of raw material oil, the supply amount of fuel oil and air, and the addition condition of oxygen gas, using an oil furnace furnace composed of a diameter reaction chamber and a wide diameter reaction chamber. is there. Note that the carbon black used in Comparative Example 1 is a small particle size carbon black that has been used in the tread rubber of a heavy duty tire as having a higher effect of improving wear resistance than in the past.

  Each rubber composition obtained was subjected to a tensile test to measure the 300% modulus, breaking strength and breaking elongation, and to evaluate the wear resistance and heat generation. Each evaluation method is as follows.

-Tensile test: 300% modulus, breaking strength and breaking elongation were measured in accordance with JIS K6251 (dumbbell shape No. 3), and displayed as an index with the value of Comparative Example 1 being 100.

Abrasion resistance: Measured in accordance with JIS K6264 (Lambourne. Standard conditions: slip rate 30%, load load 40 N, sand fall 20 g / min), and displayed as an index with the value of Comparative Example 1 being 100. It shows that it is excellent in abrasion resistance, so that an index | exponent is large.

Exothermic property: Evaluated by viscoelastic properties (tan δ at 60 ° C.). The tan δ at 60 ° C. was measured as a frequency of 10 Hz, initial elongation of 10%, and strain amplitude of 2% using a Toyo Seiki spectrometer. It shows that it is excellent in exothermic property, so that an index | exponent is small.

  As shown in Table 1, although the carbon black of Comparative Example 1 has a smaller particle size, the example using carbon black in which the pore volume between aggregates was controlled within a predetermined range was more resistant to carbon black. Abrasion was good. More specifically, in Examples 1 to 3, the wear resistance was improved by about 8% and the heat generation was also improved by 3 to 10%, which was a well-balanced example. In Example 4, the particle diameter was the same as that of Comparative Example 1 and the physical properties were also the same, but the wear resistance was improved by 6%. Furthermore, in Examples 5 and 6, the wear resistance was improved by 12 to 17%, and a significant improvement in wear resistance was observed.

  The rubber composition of the present invention can be used as a rubber composition for forming a tread portion in various heavy-duty pneumatic tires such as trucks and buses.

Claims (2)

For 100 parts by weight of diene rubber,
Carbon black having a CTAB adsorption specific surface area of 120 m ² / g or more, a compressed DBP oil absorption of 90 ml / 100 g or more, and a pore volume of 25-30 nm in the pore volume between aggregates is 30 ml / 100 g or more. A heavy load tire tread rubber composition comprising 40 to 60 parts by weight.   2. The heavy load tire tread rubber composition according to claim 1, wherein the diene rubber comprises 100 to 50% by weight of natural rubber and / or isoprene rubber and 0 to 50% by weight of butadiene rubber.