JP2016153444A - Rubber composition for tire bead insulation and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome problems of deterioration of heat generation property by a method for blending a large amount of fillers for satisfying high hardness of an insulation rubber because bead wires having largely different Young modulus are bundled and unified, and extrusion fail due to high viscosity by a method for reducing blended amount of an oil for improving heat generation property.SOLUTION: The above described problem is solved by a rubber composition for tire bead insulation by blending 100 pts.mass of a diene rubber containing a natural rubber, 80 pts.mass or more of carbon black and 20 pts.mass or more of an inorganic filler with total blended amount of them of 100 to 180 pts.mass and further 0.5 to 10 pts.mass of a styrenated phenol compound mainly containing distyrenated phenol or tristyrenated phenol.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for tire bead insulation and a pneumatic tire using the rubber composition. More specifically, the present invention has high hardness without deteriorating exothermic property, and has a viscosity when unvulcanized. The present invention relates to a rubber composition for tire bead insulation that can be kept low, and a pneumatic tire using the same.

A pneumatic tire is mainly composed of a pair of left and right bead portions and sidewall portions, and a tread portion connected to both sidewall portions, and a bead core in the bead portion is composed of a plurality of bead wires and insulation rubber covering the bead wires. Has been. Insulation rubber is required to have a high hardness in order to bundle and integrate bead wires having greatly different Young's moduli. Therefore, a method of blending a large amount of filler is used in the rubber composition for tire bead insulation.
However, such a method leads to deterioration of heat generation.
On the other hand, there is a method of reducing the blending amount of oil in order to improve the heat build-up, but there is a problem that extrusion is impossible due to high viscosity in the insulation work of the insulation rubber to the bead wire.
From the above, in the prior art, it has been very difficult to obtain a rubber composition having a high hardness and capable of maintaining a low viscosity when unvulcanized without deteriorating exothermic properties.

  Patent Document 1 listed below discloses a technique in which a rubber material is mixed with a deterioration inhibitor selected from methylene bis (alkyl sulfide) having a specific structure and a phenolic antioxidant. However, Patent Document 1 does not disclose or suggest the styrenated phenol compound of the present invention described below. In addition, a specific styrenated phenol compound is used to obtain a rubber composition that has high hardness and maintains low viscosity when unvulcanized without deteriorating exothermic properties, and this is used as a bead insulation rubber. The technical idea to be applied is not disclosed at all.

Japanese Patent Publication No. 8-26178

  An object of the present invention is to provide a rubber composition for tire bead insulation that has high hardness and can maintain a low viscosity when unvulcanized without deteriorating exothermic properties, and a pneumatic tire using the same. There is to do.

As a result of intensive studies, the present inventors have blended carbon black and inorganic filler in a specific amount with a diene rubber having a specific composition, and further blended a specific styrenated phenol compound with a specific amount. The present inventors have found that the above problems can be solved and have completed the present invention.
That is, the present invention is as follows.
1. 80 parts by mass or more of carbon black and 20 parts by mass or more of inorganic filler are blended with 100 parts by mass of diene rubber containing natural rubber and / or synthetic isoprene rubber, and the total blending amount of carbon black and inorganic filler is 100 to 180 parts by mass, and further comprising 0.5 to 10 parts by mass of a styrenated phenol compound containing distyrenated phenol or tristyrenated phenol as a main component, a rubber composition for tire bead insulation object.
2. A pneumatic tire using the rubber composition according to 1 above for bead insulation.

  According to the present invention, carbon black and an inorganic filler are blended in a specific amount with a diene rubber having a specific composition, and further, a specific styrenated phenol compound is blended in a specific amount, thereby deteriorating exothermic properties. In addition, it is possible to provide a rubber composition for tire bead insulation having a high hardness and capable of maintaining a low viscosity when unvulcanized and a pneumatic tire using the rubber composition.

Hereinafter, the present invention will be described in more detail.
(Diene rubber)
The diene rubber used in the present invention contains natural rubber (NR) and / or synthetic isoprene rubber (IR) as essential components. The blending amount of NR and / or IR is preferably 50 to 90 parts by mass, and more preferably 70 to 90 parts by mass when the entire diene rubber is 100 parts by mass. In addition to NR and IR, other diene rubbers can be used, such as butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and the like. Can be mentioned. These may be used alone or in combination of two or more. The molecular weight and microstructure are not particularly limited, and may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or may be epoxidized.

(Carbon black)
Carbon black used in the present invention, from the viewpoint of the effect of the present invention is preferably a nitrogen adsorption specific surface area _(N 2 SA) is 20 to 50 m ² / g, in the range of 25~45m ² / g Further preferred. The nitrogen adsorption specific surface area (N ₂ SA) is a value determined in accordance with JIS K6217-2. When carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of more than 50 m ² / g or less than 20 m ² / g is used, there is a risk of deterioration in insulation properties and hardness.

(Inorganic filler)
Examples of the inorganic filler used in the present invention include clay, mica, talc, shirasu, calcium carbonate, magnesium carbonate, aluminum hydroxide, and barium sulfate. The inorganic filler referred to in the present invention does not include silica.

(Styrenated phenol compound)
The styrenated phenol compound can be represented by the following formula.

  The styrenated phenol compound used in the present invention is mainly composed of distyrenated phenol in which n is 2 or tristyrenated phenol in which n is 3. The styrenated phenol compound used in the present invention can be produced by a known production method, and is also commercially available. Examples of commercially available products include SP-24 (distyrenated) manufactured by Sanko Co., Ltd. And phenol (mainly phenol), TSP (mainly tristyrenated phenol), and the like.

  Generally produced styrenated phenol compounds are monostyrenated phenols in which 1 mole of styrene is added to 1 mole of phenol (where n = 1); 2 moles of styrene are added to 1 mole of phenol. This is a mixture of distyrenated phenol (in the above formula, n = 2); tristyrenated phenol in which 3 mol of styrene is added to 1 mol of phenol (in the above formula, n = 3); and other components. In the present invention, among these styrenated phenol compounds, distyrenated phenol and tristyrenated phenol are used as main components. Since the styrenated phenol compound produced as described above is mainly a mixture of mono-, di-, and tri-isomers, the styrenated phenol compound used in the present invention can have some mono-isomers. Therefore, in the present invention, “having distyrenated phenol or tristyrenated phenol as a main component” means that distyrenated phenol or tristyrenated phenol is 50 mol% or more, preferably 60 mol% or more, more preferably It means that it occupies 65 mol% or more, and monostyrenated phenol and other components (for example, a styrenated phenol compound of a tetra-form or more) may be contained as other components.

  The styrene moiety in the above formula may be a styrene derivative. For example, α-methylstyrene, o-methylstyrene, 1,3-dimethylstyrene and the like can be mentioned.

(Rubber composition ratio)
The rubber composition of the present invention contains 80 parts by mass or more of carbon black and 20 parts by mass or more of inorganic filler with respect to 100 parts by mass of diene rubber, and the total amount of carbon black and inorganic filler is 100 to 100 parts by mass. It is 180 parts by mass, and further contains 0.5 to 10 parts by mass of a styrenated phenol compound mainly composed of distyrenated phenol or tristyrenated phenol.
Hardness falls that the compounding quantity of the said carbon black is less than 80 mass parts.
Hardness falls that the compounding quantity of the said inorganic filler is less than 20 mass parts.
If the total blending amount of the carbon black and the inorganic filler is less than 100 parts by mass, the hardness is lowered, and conversely if it exceeds 180 parts by mass, the insulation property is lowered.
When the blending amount of the styrenated phenol compound is less than 0.5 parts by mass, the blending amount is too small to achieve the effects of the present invention. Conversely, when it exceeds 10 mass parts, hardness will fall and exothermic property will also deteriorate.

A more preferable blending amount of the carbon black is 80 to 150 parts by mass with respect to 100 parts by mass of the diene rubber.
A more preferable blending amount of the inorganic filler is 90 to 130 parts by mass with respect to 100 parts by mass of the diene rubber.
The total blending amount of the carbon black and the inorganic filler is more preferably 120 to 160 parts by mass.
The blending amount of the styrenated phenol compound is more preferably 2.0 to 8.0 parts by mass (particularly preferably 4.0 to 8.0 parts by mass) with respect to 100 parts by mass of the diene rubber.

(Other ingredients)
In addition to the above-described components, the rubber composition for tire bead insulation in the present invention includes a vulcanization or cross-linking agent; a vulcanization or cross-linking accelerator; zinc oxide; an anti-aging agent; and a plasticizer for tire bead insulation. Various additives generally blended in the rubber composition can be blended, and such additives can be kneaded by a general method to form a composition, which can be used for vulcanization or crosslinking. The blending amounts of these additives can be set to conventional general blending amounts as long as the object of the present invention is not violated.

The rubber composition of the present invention has high hardness without deteriorating exothermic property, good adhesion to the bead wire, low viscosity during insulation work, and good workability. Therefore, it is suitable as a rubber composition for bead insulation.
The rubber composition of the present invention can be used to produce a pneumatic tire according to a conventional method for producing a pneumatic tire.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Examples 1-3 and Comparative Examples 1-7
Sample preparation In the formulation (parts by mass) shown in Table 1, the components except the vulcanization accelerator and sulfur were kneaded for 5 minutes in a 1.7 liter closed Banbury mixer, then the rubber was discharged outside the mixer and cooled to room temperature. I let you. Thereafter, a vulcanization accelerator and sulfur were added to the rubber with the same Banbury mixer and further kneaded to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized in a predetermined mold at 148 ° C. for 45 minutes to obtain a vulcanized rubber test piece, and an unvulcanized rubber composition and vulcanized rubber were tested by the following test method. The physical properties of the test piece were measured.

Hardness (20 ° C.): Measured at 20 ° C. based on JIS K6253. The results are shown as an index with the value of Comparative Example 1 being 100. The larger the index, the higher the hardness.
Exothermic property: Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, tan δ (60 ° C.) was measured under the conditions of initial strain 10%, amplitude ± 2%, frequency 20 Hz, and temperature 60 ° C. The results are shown as an index with the value of Comparative Example 1 being 100. A smaller index indicates a lower exothermic property.
Mooney bis: The viscosity of the unvulcanized rubber composition at 100 ° C. was measured according to JIS K6300. The result was expressed as an index with the value of Comparative Example 1 as 100. The smaller the index, the lower the viscosity and the better the workability.
Insulation property: The obtained rubber composition was applied to a tinned bead wire (φ1.55 mm) at a thickness of 2.0 mm using a pneumatic tire bead manufacturing apparatus disclosed in Japanese Patent No. 4979588. After coating, the rubber adhesion rate to the bead wire surface was visually scored from 0 to 100%. The index of Comparative Example 1 was expressed as 100. The larger the index, the better the insulation property.
The results are also shown in Table 1.

* 1: NR (RSS # 3)
* 2: SBR (Nipol 1502 manufactured by Zeon Corporation)
* 3: Carbon black (HTC-100 (FEF) manufactured by Nippon Kayaku Co., Ltd., nitrogen adsorption specific surface area (N ₂ SA) = 41 m ² / g)
* 4: Calcium carbonate (M-300 manufactured by Maruo Calcium Co., Ltd.)
* 5: Zinc oxide (3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd.)
* 6: Stearic acid (Stearic acid YR manufactured by NOF Corporation)
* 7: Sulfur (Karuizawa Smelter Refinery sulfur)
* 8: Vulcanization accelerator DZ (Noxeller DZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 9: Anti-aging agent (Santoflex 6PPD manufactured by FLEXSYS)
* 10: Aroma oil (Extract No. 4 S manufactured by Showa Shell Sekiyu KK)
* 11: Styrenated phenol compound-1 (SP-F manufactured by Sanko Co., Ltd. Monostyrenated phenol 65 mol% or more, distyrenated phenol 32 mol% or less, tristyrenated phenol 1 mol% or less)
* 12: Styrenated phenol compound-2 (SP-24 manufactured by Sanko Co., Ltd. Monostyrenated phenol 0 mol%, distyrenated phenol 60 mol% or more, tristyrenated phenol 40 mol% or less)
* 13: Styrenated phenol compound-3 (TSP manufactured by Sanko Co., Ltd. Monostyrenated phenol 0 mol%, distyrenated phenol 30 mol% or less, tristyrenated phenol 65 mol% or more)

As apparent from Table 1 above, the rubber compositions prepared in Examples 1 to 3 were prepared by blending carbon black and an inorganic filler in specific amounts with a diene rubber having a specific composition, and further adding specific styrene. Since the compounded phenolic compound is blended with a specific amount, it has high hardness and can maintain a low viscosity when not vulcanized without deteriorating exothermicity as compared with the conventional representative comparative example 1. I understand that.
In contrast, in Comparative Example 2, the amount of carbon black was less than the lower limit specified in the present invention, so the hardness was lowered.
In Comparative Example 3, since the blending amount of the inorganic filler was less than the lower limit specified in the present invention, the hardness decreased.
Since the comparative example 4 is an example in which the diene rubber is composed of SBR, the heat generation property is deteriorated.
Since the comparative example 5 uses the styrenated phenol compound which has monostyrenated phenol as a main component, hardness fell.
In Comparative Example 6, since the blending amount of the specific styrenated phenol compound exceeded the upper limit specified in the present invention, the hardness was lowered and the heat generation was also deteriorated.
In Comparative Example 7, the total blending amount of bon black and the inorganic filler exceeds the upper limit defined in the present invention, so exothermicity is deteriorated, viscosity at the time of unvulcanization is high, and insulation properties are also deteriorated. .

Claims (2)

  80 parts by mass or more of carbon black and 20 parts by mass or more of inorganic filler are blended with 100 parts by mass of diene rubber containing natural rubber and / or synthetic isoprene rubber, and the total blending amount of carbon black and inorganic filler is 100 to 180 parts by mass, and further comprising 0.5 to 10 parts by mass of a styrenated phenol compound containing distyrenated phenol or tristyrenated phenol as a main component, a rubber composition for tire bead insulation object.   A pneumatic tire using the rubber composition according to claim 1 for bead insulation.