JP2022098226A - Rubber composition for tire tread, and pneumatic tire - Google Patents

Abstract

To provide a rubber composition for a tire tread, which serves as a raw material of a pneumatic tire excellent in balance between rubber hardness and elongation of a tire tread.SOLUTION: The rubber composition for a tire tread contains a rubber component, a filler, and a layered or plate-like mineral having an aspect ratio of 5 or more. When the content of the filler is 100, the content of the mineral is 1-10. When the total amount of the rubber component is 100 pts.mass, the content of the mineral is preferably 4.5 pts.mass or less. The aspect ratio of the mineral is preferably 100 or more.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition for a tire tread, and in particular, a rubber composition as a raw material for a pneumatic tire having a tire tread having an excellent balance between rubber hardness and elongation, and a rubber composition for the tire tread are vulture-molded. With respect to pneumatic tires with rubber treads.

Generally, in order to improve the steering stability of a pneumatic tire, there is a method of increasing the rubber hardness of the rubber portion constituting the tire tread. As a method of increasing the rubber hardness, for example, there is a method of increasing the amount of filler such as carbon black, but along with this, the elongation of the rubber portion constituting the tire tread is lowered, and the durability of the pneumatic tire tends to be deteriorated.

The following Patent Document 1 describes a rubber composition for an inner liner containing 10 to 50 parts by weight of mica having an aspect ratio of 50 or more and an average particle size of 40 to 100 μm.

Further, Patent Document 2 below describes a rubber composition characterized by blending a layered clay mineral and a phenolic resin with respect to a rubber component.

Further, in Patent Document 3 below, a heavy-duty tire provided with a tire side portion in which a rubber composition containing 0.1 to 30 parts by mass of an orientation material oriented in the tire circumferential direction is arranged with respect to 100 parts by mass of the rubber component is provided. Have been described.

Japanese Unexamined Patent Publication No. 2006-328193 Japanese Unexamined Patent Publication No. 2008-189725 WO2013 / 094147

However, as a result of diligent studies by the present inventor, it has been found that the techniques described in any of the above documents have room for further improvement in terms of improving the balance between the rubber hardness and elongation of the tire tread.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber composition for a tire tread, which is a raw material for a pneumatic tire having an excellent balance between the rubber hardness and elongation of the tire tread. ..

The above problem can be solved by the following configuration. That is, the present invention contains a rubber component, a filler, and a layered or plate-shaped mineral having an aspect ratio of 5 or more, and when the content of the filler is 100, the content of the mineral is 1 to 10. The present invention relates to a rubber composition for a tire tread.

In the rubber composition for tire tread, when the total amount of the rubber component is 100 parts by mass, the content of the mineral is preferably 4.5 parts by mass or less.

In the rubber composition for tire tread, the aspect ratio of the mineral is preferably 100 or more.

The present invention also relates to a pneumatic tire provided with a rubber portion formed by vulcanizing the rubber composition for tire tread according to any one of the above.

In the present invention, since a specific amount of a mineral having a specific aspect ratio is blended with the filler in the rubber composition for tire tread, the rubber portion constituting the tire tread manufactured from the rubber composition is made of rubber. Excellent balance between hardness and elongation. Therefore, the pneumatic tire provided with the tire tread manufactured from the rubber composition for tire tread according to the present invention is excellent in steering stability and durability. In particular, when the total amount of rubber components in the rubber composition for tire tread is 100 parts by mass and the content of minerals having an aspect ratio of 100 or more is set to 4.5 parts by mass or less with respect to the filler. The rubber portion constituting the tire tread manufactured from the rubber composition as a raw material has a particularly excellent balance between rubber hardness and elongation.

The rubber composition for tire tread according to the present invention contains a rubber component, a filler, and a layered or plate-shaped mineral having an aspect ratio of 5 or more.

The rubber composition for tire tread according to the present invention preferably contains a diene-based rubber as a rubber component. Examples of the diene rubber include natural rubber (NR), polyisoprene rubber (IR), polybutadiene (BR), polystyrene butadiene rubber (SBR), chloroprene rubber (CR), and nitrile rubber (NBR).

The rubber composition for tire tread according to the present invention may contain, for example, carbon black and silica as fillers.

As the carbon black, for example, in addition to carbon black used in the ordinary rubber industry such as SAF, ISAF, HAF, FEF, and GPF, conductive carbon black such as acetylene black and Ketjen black can be used. The rubber composition for a tire tread according to the present invention preferably contains 30 to 70 parts by mass of carbon black, more preferably 40 to 60 parts by mass, with respect to 100 parts by mass of diene-based rubber.

As the silica, wet silica, dry silica, sol-gel silica, surface-treated silica and the like used for ordinary rubber reinforcement are used. Of these, wet silica is preferable. The blending amount of silica in the rubber composition for tire tread according to the present invention is preferably about the same as that of carbon black.

When silica is blended, it is preferable to use a silane coupling agent in combination. The silane coupling agent is not particularly limited as long as it contains sulfur in the molecule, and various silane coupling agents blended with silica in the rubber composition can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide (eg, "Si69" manufactured by Degusa), bis (3-triethoxysilylpropyl) disulfide (eg, "Si75" manufactured by Degusa), bis (2-tri). Propylsilanes such as ethoxysilylethyl) tetrasulfide, bis (4-triethylsilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide, γ-mercaptopropyltri Mercaptosilanes such as methoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane, 3-octanoylthio-1-propyltriethoxysilane, 3-propionylthiopropyltri Protected mercaptosilanes such as methoxysilane can be mentioned.

The rubber composition for tire tread according to the present invention contains a layered or plate-shaped mineral having an aspect ratio of 5 or more. When a mineral having an aspect ratio of 100 or more is blended in the rubber composition, the rubber portion produced from the rubber composition as a raw material has a particularly excellent balance between rubber hardness and elongation. Examples of minerals having such an aspect ratio include talc.

In the rubber composition for tire tread according to the present invention, when the content of the filler is 100, the blending amount of the mineral is set to 1 to 10. When the total amount of the rubber component is 100 parts by mass and the blending amount of the mineral is set to 4.5 parts by mass or less, the rubber part produced from the rubber composition as a raw material has a balance between rubber hardness and elongation. Especially excellent. When the total amount of the rubber component is 100 parts by mass, the lower limit of the blending amount of the mineral is preferably 0.5 parts by mass or more, and more preferably 2.5 parts by mass or more.

In the rubber composition for tire tread according to the present invention, a vulcanization compound, an antiaging agent, zinc oxide, stearic acid, and wax are used together with a rubber component, a filler, and a layered or plate-shaped mineral having an aspect ratio of 5 or more. , And softeners such as oil, processing aids, etc. can be blended.

Examples of the vulcanization-based compounding agent include vulcanization agents such as sulfur and organic peroxides, vulcanization accelerators, vulcanization acceleration aids, and vulcanization retarders.

The sulfur as the vulcanization-based compounding agent may be ordinary sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used.

As the vulcanization accelerator, a sulfur amide-based vulcanization accelerator, a thiuram-based vulcanization accelerator, a thiazole-based vulcanization accelerator, a thiourea-based vulcanization accelerator, and a guanidine-based vulcanization agent, which are usually used for rubber vulcanization, are used. A vulcanization accelerator such as an accelerator or a dithiocarbamate-based vulcanization accelerator may be used alone or in combination as appropriate.

As anti-aging agents, aromatic amine-based anti-aging agents, amine-ketone anti-aging agents, monophenol anti-aging agents, bisphenol anti-aging agents, polyphenol anti-aging agents, dithiocarbamic acid, which are usually used for rubber. Anti-aging agents such as salt-based anti-aging agents and thiourea-based anti-aging agents may be used alone or in admixture.

The rubber composition according to the present invention includes a rubber component, a filler, a layered or plate-shaped mineral having an aspect ratio of 5 or more, a silane coupling agent, a vulcanization-based compounding agent, an antioxidant, zinc oxide, and stear. It is obtained by kneading softeners such as acids, waxes and oils, processing aids and the like using a kneader used in a normal rubber industry such as a Banbury mixer, a kneader and a roll.

The compounding method of each of the above components is not particularly limited, and compounding components other than the sulfur-based compounding agent such as a sulfur-based vulcanizing agent and a vulcanization accelerator are kneaded in advance to form a masterbatch, and the remaining components are added. Then, a method of further kneading, a method of adding each component in an arbitrary order and kneading, a method of adding all the components at the same time and kneading, and the like may be used.

The vulcanized rubber of the rubber composition for tire tread according to the present invention has a particularly excellent balance between rubber hardness and elongation. Therefore, a pneumatic tire including a tire tread composed of a rubber portion formed by vulcanizing a rubber composition for a tire tread is particularly excellent in steering stability and durability.

Hereinafter, examples and the like that specifically show the configuration and effect of the present invention will be described. As the evaluation items in Examples and the like, the rubber samples obtained by heating each rubber composition at 150 ° C. for 30 minutes and vulcanizing were evaluated based on the following evaluation conditions.

(1) Rubber hardness For the evaluation of rubber hardness, the hardness of the obtained vulcanized rubber test piece was measured at a temperature of 23 ° C. using a durometer type A in accordance with JIS K6253, and the value of Comparative Example 1 was used. It was displayed as an index of 100. The larger the index, the higher the hardness at room temperature and the better the rubber hardness.

(2) Elongation According to JIS K6251, a sample was prepared using dumbbell No. 3 and a tensile test was performed, and the elongation at break (%) at the time of breaking the sample was measured. The measured value of Comparative Example 1 is set to 100 and displayed by exponential evaluation, and the larger the value, the better the elongation.

(Preparation of rubber composition)
The rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were blended according to the formulation in Table 1 and kneaded using a normal Banbury mixer to prepare the rubber composition. Each compounding agent shown in Table 1 is shown below (in Table 1, the compounding amount of each compounding agent is shown by the number of parts by mass with respect to 100 parts by mass of the rubber component).
a) Natural rubber (NR): Product name "RSS # 3"
b) Carbon black: Product name "Seast 6" manufactured by Tokai Carbon Co., Ltd. c) Zinc oxide: Product name "Zinc oxide type 1" manufactured by Mitsui Kinzoku Mine Co., Ltd. d) Stealic acid: Product name "Bead stearic acid" manufactured by Nichiyu Co., Ltd. e ) Anti-aging agent: Product name "Santflex 6PPD", manufactured by Flexsys f) Minerals (1) (Tark): Product name "HAR", aspect ratio 143, g) minerals (2) (clay) ): Product name "polyfil DL", aspect ratio 12.7, KAMIN. LLC h) Minerals (3) (Clay): Trade name "polyfil DLX", aspect ratio 13.5, KAMIN. LLC i) Vulcanization accelerator TBBS: Product name "Sunceller NS-G", manufactured by Sanshin Chemical Industry Co., Ltd. j) Sulfur: Product name "Powdered sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.

From the results in Table 1, it can be seen that in the rubber composition according to Comparative Example 2, the rubber hardness of the vulcanized rubber increases as the amount of the filler (carbon black) increases, but the elongation deteriorates. On the other hand, it can be seen that the rubber compositions according to Examples 1 to 4 containing minerals (talc or clay) having an aspect ratio of 5 or more improve the rubber hardness and elongation of the vulcanized rubber in a well-balanced manner. In particular, when the total amount of the rubber component of a mineral (talc) having an aspect ratio of 100 or more is 100 parts by mass, Examples 3 to 4 adjusted to 4.5 parts by mass or less show the rubber hardness and elongation of the vulcanized rubber. It can be seen that is particularly well-balanced.

Claims (4)

For tire treads containing a rubber component, a filler, and a layered or plate-shaped mineral having an aspect ratio of 5 or more, and the mineral content is 1 to 10 when the filler content is 100. Rubber composition. The rubber composition for tire tread according to claim 1, wherein the content of the mineral is 4.5 parts by mass or less when the total amount of the rubber component is 100 parts by mass. The rubber composition for a tire tread according to claim 1 or 2, wherein the mineral has an aspect ratio of 100 or more. A pneumatic tire comprising a tire tread obtained by vulcanizing and molding the rubber composition for a tire tread according to any one of claims 1 to 3.