JP2008303334A - Rubber composition for cap tread, and tire with cap tread using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a cap tread enhancing performance on ice and snow without worsening abrasion resistance, and a pneumatic tire and a studless tire having the cap tread using the rubber composition. <P>SOLUTION: This rubber composition of the present invention contains 0.5-20 pts.wt. of potassium titanate fiber, and 5-200 pts.wt. of carbon black having 100-300 mg/g of iodine adsorption amount, with respect to 100 pts.wt. of rubber component comprising natural rubber and butadiene rubber. The pneumatic tire is provided using the rubber composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for a cap tread and a pneumatic tire and a studless tire having a cap tread using the same.

  Conventionally, spike tires have been used for running on snowy and snowy roads, and chains have been attached to tires. However, when these are used, the road surface is shaved by metal pins of spike tires or chains wound around tires. Since problems such as the dust problem that the road surface material flies in the air occur, studless tires have been proposed as icy and snowy road surface tires to replace spike tires.

  In ordinary tires, the friction coefficient is remarkably reduced on an icy and snowy road surface as compared with a general road surface, and the tire is easy to slip. Therefore, the studless tire is devised in terms of material and design. For example, development of rubber compositions containing diene rubbers with excellent low-temperature properties, innovations that change the surface irregularities of the tire surface to increase surface edge components, and blending of inorganic fillers and fibers that have a scratching effect have been carried out. It was.

  However, even if the above-described technique is used, the studless tire has a problem that the friction performance on the icy and snowy road surface is inferior to the spiked tire.

  In Patent Document 1, in addition to a rubber component, glass fiber, and a reinforcing agent, by adding a predetermined amount of inorganic powder that is softer than glass fiber and has a predetermined average particle diameter, it is reinforced without increasing the hardness of the rubber. Although a tread rubber composition for tires has been disclosed in which the dispersibility of the agent is maintained and the performance on ice and the wear resistance are improved, there is room for improvement in performance on ice.

JP 2002-30183 A

  An object of the present invention is to provide a rubber composition for a cap tread capable of improving the performance on ice and snow without reducing wear resistance, and a pneumatic tire and a studless tire having the cap tread using the same. To do.

  The present invention relates to 0.5 to 20 parts by weight of potassium titanate fiber and 100 to 300 mg / g of carbon black having an iodine adsorption of 100 to 300 mg / g with respect to 100 parts by weight of a rubber component composed of natural rubber and butadiene rubber. The present invention relates to a rubber composition for cap treads containing 200 parts by weight.

  The present invention also relates to a pneumatic tire using the cap tread rubber composition as a cap tread.

  The present invention also relates to a studless tire using the cap tread rubber composition for a cap tread.

  According to the present invention, by containing a specific amount of a natural rubber and a butadiene rubber, a specific carbon black, and a potassium titanate fiber, the performance on snow and ice can be improved without reducing wear resistance. It is possible to provide a rubber composition for a cap tread that can be used, and a pneumatic tire and a studless tire having a cap tread using the rubber composition.

  The rubber composition of the present invention includes a rubber component composed of natural rubber (NR) and butadiene rubber (BR), carbon black, and potassium titanate fibers.

  The rubber component has excellent properties at low temperatures (excellent low temperature characteristics) required for studless tire treads, such as embrittlement characteristics and ice wet grip characteristics, and is constant even in soft studless tire treads. NR and BR are used for the reason that the reinforcing property can be maintained and the processability is excellent.

  The content of NR in the rubber component is preferably 10% by weight or more, and more preferably 20% by weight or more. If the NR content is less than 10% by weight, the processability tends to deteriorate. The NR content in the rubber component is preferably 90% by weight or less, and more preferably 80% by weight or less. When the content ratio of NR exceeds 90% by weight, the low-temperature characteristics necessary for the tread of the studless tire cannot be maintained, and the tire performance (snow performance) on the icy and snowy road surface tends to be significantly deteriorated.

  The BR content in the rubber component is preferably 10% by weight or more, and more preferably 20% by weight or more. If the BR content is less than 10% by weight, the low-temperature characteristics required for the tread of the studless tire cannot be maintained, and the snow performance tends to be greatly deteriorated. Further, the BR content in the rubber component is preferably 90% by weight or less, and more preferably 80% by weight or less. When the BR content exceeds 90% by weight, the workability tends to deteriorate.

  As BR, 1,4-cis BR, 1,4-trans BR, etc. which are usually used in the rubber industry can be used.

  As rubber components, in addition to NR and BR, diene rubbers commonly used in the rubber industry, such as isoprene rubber (IR), styrene butadiene rubber (SBR), butyl rubber (IIR), chloroprene rubber (CR), acrylonitrile butadiene Rubber (NBR), ethylene propylene diene rubber (EPDM), styrene isoprene butadiene rubber (SIBR), etc. can be blended, but rubber components other than NR and BR may not be used because processability deteriorates. preferable.

  The iodine adsorption amount (IA) of carbon black is 100 mg / g or more, preferably 110 mg / g or more. If the IA of the carbon black is less than 100 mg / g, the reinforcing property is lowered. The IA of carbon black is 300 mg / g or less, preferably 250 mg / g or less. When the IA of the carbon black exceeds 300 mg / g, the low heat buildup and durability are lowered, and the workability is deteriorated.

  The content of carbon black is 5 parts by weight or more, preferably 10 parts by weight or more with respect to 100 parts by weight of the rubber component. When the carbon black content is less than 5 parts by weight, the reinforcing effect is lowered. The carbon black content is 200 parts by weight or less, preferably 100 parts by weight or less, based on 100 parts by weight of the rubber component. If the carbon black content exceeds 200 parts by weight, the processability deteriorates.

  Potassium titanate fibers have many features such as high strength, high rigidity, and high aspect ratio, and are generally used in a wide range of applications such as plastic and metal reinforcements, automotive friction materials, and precision filters.

  The fiber diameter of the potassium titanate fiber is preferably 0.2 μm or more, and more preferably 0.3 μm or more, because it is difficult to produce potassium titanate fibers of less than 0.2 μm. In addition, the fiber diameter of the potassium titanate fiber is preferably 0.6 μm or less, more preferably 0.5 μm or less, from the viewpoint of excellent wear resistance.

  The fiber length of the potassium titanate fiber is preferably 10 μm or more, more preferably 12 μm or more, from the viewpoint that the ice scratching effect is excellent. The fiber length of the potassium titanate fiber is preferably 20 μm or less, and preferably 18 μm or less from the viewpoint of excellent wear resistance.

  The ratio of the average fiber length to the average fiber diameter of the potassium titanate fibers (average aspect ratio, (average fiber length) / (average fiber diameter)) is not particularly limited, and is generally about 20 to 40 after kneading. .

  The content of the potassium titanate fiber is 0.5 parts by weight or more, preferably 1 part by weight or more with respect to 100 parts by weight of the rubber component. When the content of potassium titanate fiber is less than 0.5 parts by weight, the amount of potassium titanate fiber that falls off is more than that retained during compounding, and the effect of digging up snow and snow caused by potassium titanate fiber is reduced. Performance decreases. The content of the potassium titanate fiber is 20 parts by weight or less, preferably 15 parts by weight or less with respect to 100 parts by weight of the rubber component. When the content of the potassium titanate fiber exceeds 20 parts by weight, the wear resistance decreases.

  In the present invention, the grip performance on ice can be improved by containing a specific amount of a rubber component composed of natural rubber and butadiene rubber, specific carbon black, and potassium titanate fiber.

  In addition to the rubber component, carbon black, and potassium titanate fiber, the rubber composition of the present invention includes compounding agents conventionally used in the rubber industry, for example, reinforcing fillers other than carbon black such as silica, and various oils. In addition, softening agents such as wax, various anti-aging agents, vulcanizing agents such as stearic acid, zinc oxide, and sulfur, various vulcanization accelerators, and the like can be appropriately blended as necessary.

  The tread portion of the pneumatic tire of the present invention preferably has a two-layer structure consisting of a cap tread and a base tread instead of a one-layer structure, and the rubber composition of the present invention is excellent in wear resistance and friction performance on ice. Therefore, it is preferable to use it for a cap tread.

  The pneumatic tire of the present invention can be produced by a usual method using the rubber composition of the present invention. That is, if necessary, the rubber composition of the present invention blended with the above-mentioned compounding agent is extruded in accordance with the shape of the cap tread of the tire at an unvulcanized stage, and on the tire molding machine together with other components of the tire. An unvulcanized tire is molded by molding in a conventional manner. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain the pneumatic tire of the present invention.

  The pneumatic tire of the present invention thus obtained is preferably a studless tire because the improvement in performance on ice can be expected.

  The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

The various chemicals used in the present invention are shown below.
Natural rubber (NR): RSS # 3 manufactured by Tech Bee Hang
Butadiene rubber (BR): Ubepol BR150B manufactured by Ube Industries, Ltd.
Carbon black: Show black N220 manufactured by Cabot Japan Co., Ltd. (Iodine adsorption amount: 119 mg / g)
Potassium titanate fiber: Tismo D manufactured by Otsuka Chemical Co., Ltd. (fiber length: 10 to 20 μm, fiber diameter: 0.3 to 0.6 μm, aspect ratio after kneading: 20 to 40)
Anti-aging agent: NOCRACK 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Wax: Sunnock wax oil manufactured by Ouchi Shinsei Chemical Industry Co., Ltd .: Dyna Process Oil PS323 manufactured by Idemitsu Kosan Co., Ltd.
Stearic acid: Zinc stearate manufactured by Nippon Oil & Fats Co., Ltd .: Zinc flower No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide)
Vulcanization accelerator 2: Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-2 and Comparative Examples 1-3
According to the formulation shown in Table 1, first, the compounding agent excluding sulfur and the vulcanization accelerator was kneaded for 3 to 5 minutes using a closed banbury mixer with a capacity of 1.7 L until the temperature reached 150 ° C. A kneaded product was obtained. Sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 2 minutes at 70 ° C. using an open roll to obtain an unvulcanized rubber composition. Furthermore, the obtained unvulcanized rubber composition was molded into a predetermined size, and vulcanized rubber tests of Examples 1-2 and Comparative Examples 1-3 were performed by press vulcanization at 170 ° C. for 12 minutes. I got a piece.

<Friction performance on ice>
Friction coefficient (friction on ice) when the vulcanized rubber test piece is pressed at 2 kg / cm ² on the ice surface of −2 ° C. installed in a temperature controlled temperature chamber of −5 ° C. and slid at 20 km / hour. The coefficient of friction on ice of Comparative Example 1 was set to 100, and the coefficient of friction on ice of each formulation was displayed as an index according to the following formula. The larger the on-ice friction performance index, the higher the on-ice friction performance and the better on-ice performance.
(Friction performance index on ice) = (Friction coefficient on ice for each formulation)
÷ (Friction coefficient on ice of Comparative Example 1) × 100

<Abrasion resistance>
The unvulcanized rubber composition is formed into a cap tread shape by a calender roll by a commonly used method, bonded to another tire member, and press vulcanized at 170 ° C. for 12 minutes, thereby being studless. A tire (tire size: 195 / 65R15) was produced.

The tire was mounted on a domestic FF vehicle, and a general asphalt road was run for 8000 km, and the groove depth of the tread portion of the tire was measured. Furthermore, from the measured groove depth, the travel distance required for the groove depth of the tread portion to be reduced by 1 mm was calculated, and the abrasion resistance index of Comparative Example 1 was set to 100. The mileage is displayed as an index. The larger the wear resistance index, the better the wear resistance.
(Abrasion resistance index) = (travel distance of each formulation) ÷ (travel distance of Comparative Example 1) × 100

  The evaluation results are shown in Table 1.

Claims (3)

Contains 0.5 to 20 parts by weight of potassium titanate fiber and 5 to 200 parts by weight of carbon black having an iodine adsorption of 100 to 300 mg / g with respect to 100 parts by weight of a rubber component made of natural rubber and butadiene rubber. A rubber composition for cap treads. A pneumatic tire using the rubber composition according to claim 1 for a cap tread. A studless tire using the rubber composition according to claim 1 for a cap tread.