JP2008007678A - Rubber composition for cap tread, and pneumatic tire having cap tread composed of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a cap tread that can enhance on-ice/snow performances without deteriorating abrasion resistance and a pneumatic tire having a cap tread composed of the same. <P>SOLUTION: The rubber composition for a cap tread comprises 100 pts.wt. of at least one diene rubber selected from the group consisting of a natural rubber, an isoprene rubber, a styrene-butadiene rubber and a butadiene rubber, 5-200 pts.wt. of carbon black having an iodine adsorption number of 100-300 mg/g and 0.5-22 pts.wt. of a bamboo fiber, and contains 1-20 pts.wt. of a silane coupling agent based on 100 pts.wt. of the bamboo fiber. The tire has a cap tread composed of the same. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for a cap tread and a pneumatic 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 that can improve the performance on ice and snow without lowering the wear resistance, and a pneumatic tire having a cap tread using the same.

  The present invention relates to carbon black having an iodine adsorption of 100 to 300 mg / g with respect to 100 parts by weight of at least one diene rubber selected from the group consisting of natural rubber, isoprene rubber, styrene butadiene rubber and butadiene rubber. The present invention relates to a rubber composition for a cap tread containing 5 to 200 parts by weight and 0.5 to 22 parts by weight of bamboo fiber and 1 to 20 parts by weight of a silane coupling agent with respect to 100 parts by weight of the bamboo fiber.

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

  According to the present invention, by containing a predetermined amount of a predetermined rubber component, a predetermined carbon black, bamboo fiber, and a silane coupling agent, a cap capable of improving the performance on ice and snow without reducing wear resistance. A rubber composition for a tread and a pneumatic tire having a cap tread using the same can be provided.

  The rubber composition for a cap tread of the present invention includes a diene rubber component, carbon black, bamboo fiber, and a silane coupling agent.

  As the diene rubber component, natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR) and butadiene rubber (for the reason that excellent low temperature characteristics are required for the tread of a studless tire. At least one diene rubber selected from the group consisting of BR) is used. Among these, NR and / or BR are preferable, and NR and BR are more preferable because a certain reinforcing property can be maintained even in a tread of a soft studless tire.

  When NR is used, the content of NR in the diene 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 is preferably 90% by weight or less, and more preferably 80% by weight or less. If the NR content exceeds 90% 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.

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

  When BR is used, the BR content in the diene 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. The BR content is preferably 90% by weight or less, more preferably 80% by weight or less. When the BR content exceeds 90% by weight, the workability tends to deteriorate.

  As diene rubber components, in addition to NR, IR, SBR and BR, diene rubbers commonly used in the rubber industry such as butyl rubber (IIR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), ethylene Examples include propylene diene rubber (EPDM) and styrene isoprene butadiene rubber (SIBR). However, it is preferable not to use a diene rubber other than NR, IR, SBR and BR because the processability is deteriorated.

  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 diene 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. If the carbon black content exceeds 200 parts by weight, the processability deteriorates.

  In addition to bamboo fiber, there are paper fiber, glass fiber, carbon fiber, cellulose fiber, synthetic fiber, etc., but in consideration of the global environment, in preparation for the future decrease in oil supply, and natural fiber Bamboo fiber is used because it has excellent rigidity while being a fiber.

  The bamboo fibers are preferably oriented in the thickness direction of the tread for the purpose of maximizing the braking and starting effects.

  Bamboo fibers are not particularly limited, but include those obtained from natural bamboo.

  The average fiber diameter of the bamboo fiber after kneading is preferably 10 μm or more, and more preferably 15 μm or more. If the average fiber diameter of the bamboo fibers after kneading is less than 10 μm, the bending resistance performance tends to decrease, and the effect of digging up snow and snow tends to decrease. Moreover, the average fiber diameter of the bamboo fiber after kneading is preferably 100 μm or less, and more preferably 70 μm or less. When the average fiber diameter of the bamboo fibers after kneading exceeds 100 μm, the contact area between the rubber and the ice surface decreases, and the friction performance on ice tends to decrease. Furthermore, there is a tendency to cause poor dispersion and wear resistance.

  The average fiber length of the bamboo fiber after kneading is preferably 0.1 mm or more, and more preferably 0.2 mm or more. If the average fiber length of the bamboo fibers after kneading is less than 0.1 mm, the bamboo fibers fall off from the tread surface, and the performance on ice and snow tends to deteriorate. Further, the average fiber length of the bamboo fibers after kneading is preferably 2 mm or less, and more preferably 1.5 mm or less. When the average fiber length of the bamboo fibers after kneading exceeds 2 mm, the workability in the process tends to deteriorate (handling becomes difficult).

  The ratio of the average fiber length to the average fiber diameter of the bamboo fibers after kneading (average aspect ratio, (average fiber length) / (average fiber diameter)) is preferably 20 or more, and more preferably 30 or more. If the average aspect ratio of the bamboo fibers after kneading is less than 20, the bamboo fibers fall off from the tread surface, and the performance on ice and snow tends to deteriorate. Further, the average aspect ratio of the bamboo fiber after kneading is preferably 50 or less, and more preferably 40 or less. Few bamboo fibers have an average aspect ratio exceeding 50 after kneading. In general, when bamboo fiber is blended and kneaded, the average aspect ratio of bamboo fiber is in the range of 30-40.

  The content of the bamboo fiber is 0.5 parts by weight or more, preferably 2 parts by weight or more with respect to 100 parts by weight of the diene rubber. If the bamboo fiber content is less than 0.5 parts by weight, the effect of digging up ice and snow by the fiber will be reduced, and the performance on ice and snow will be reduced. The bamboo fiber content is 22 parts by weight or less, preferably 20 parts by weight or less. When the bamboo fiber content exceeds 22 parts by weight, the wear resistance is lowered.

  The silane coupling agent is not particularly limited as long as it is conventionally blended in a rubber composition. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxy) Silylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) ) Tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide Sulfide, bis (2-to Rimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) ) Disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl Tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl- , N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate Sulfide series such as monosulfide, mercapto series such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyltriethoxysilane, vinyltri Vinyl type such as methoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) a Amino compounds such as nopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyl Glycidoxy type such as methyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloro Examples include chloro-based compounds such as propyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane.

  The content of the silane coupling agent is 1 part by weight or more, preferably 2 parts by weight or more with respect to 100 parts by weight of bamboo fiber. If content of a silane coupling agent is less than 1 weight part, the effect by mix | blending a silane coupling agent will not be seen, but abrasion resistance will fall. The content of the silane coupling agent is 20 parts by weight or less, preferably 15 parts by weight or less. When the content of the silane coupling agent exceeds 20 parts by weight, the effect of increasing the amount of the silane coupling agent is not obtained for an increase in cost, and the reinforcement and wear resistance are lowered.

  In the present invention, the grip performance on ice can be improved by containing a predetermined amount of a predetermined rubber component, a predetermined carbon black, bamboo fiber, and a silane coupling agent.

  In addition to the rubber component, carbon black, bamboo fiber, and silane coupling agent, the rubber composition for cap tread of the present invention is filled with a compounding agent conventionally used in the rubber industry, such as silica other than carbon black. Agents, softeners such as various oils and waxes, 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 pneumatic tire of the present invention can be produced by a usual method using the rubber composition for a cap tread of the present invention. That is, the rubber composition for a cap tread of the present invention blended with the above-mentioned compounding agent as necessary is extruded in accordance with the shape of the tire cap tread in an unvulcanized stage, and together with other members of the tire, the tire An unvulcanized tire is molded by molding on a molding machine by a normal method. 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.

  EXAMPLES Although this invention is demonstrated in detail based on an Example, this invention is not limited only to these Examples.

Next, the chemical | medical agent used by the Example and the comparative example is demonstrated.
Natural rubber (NR): RSS # 3
Butadiene rubber (BR): UBEPOL-BR150B manufactured by Ube Industries, Ltd.
Carbon Black: Show Black N220 (IA: 121 mg / g) manufactured by Cabot Japan
Bamboo fiber: prototype (produced by crushing natural bamboo, average fiber diameter: 30 μm, average fiber length: 3 mm, average aspect ratio: 100)
Oil: Diana Process Oil PS323 manufactured by Idemitsu Kosan Co., Ltd.
Wax: Sunnock wax anti-aging agent manufactured by Ouchi Shinsei Chemical Industry Co., Ltd .: NOCRACK 6C (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shin Chemical Co., Ltd. )
Stearic acid: Zinc flower manufactured by NOF Corporation: Zinc flower No. 1 silane coupling agent manufactured by Mitsui Mining & Smelting Co., Ltd .: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Sulfur: powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. (1): Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator (2): Noxeller D (diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-3 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 to 3 and Comparative Examples 1 to 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 was pressed at 2 kg / cm ² and slid at 20 km / h on the ice surface of −2 ° C. installed in a temperature-controlled room controlled at −5 ° C. 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 expressed 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 (2)

For 100 parts by weight of at least one diene rubber selected from the group consisting of natural rubber, isoprene rubber, styrene butadiene rubber and butadiene rubber,
Containing 5 to 200 parts by weight of carbon black having an iodine adsorption amount of 100 to 300 mg / g, and 0.5 to 22 parts by weight of bamboo fiber;
A rubber composition for a cap tread containing 1 to 20 parts by weight of a silane coupling agent with respect to 100 parts by weight of the bamboo fiber. A pneumatic tire having a cap tread using the rubber composition for a cap tread according to claim 1.