JP2002020549A - Rubber filler for tire molding and its use - Google Patents

Abstract

(57) [Problem] To provide a bladder for tire vulcanization and a tire tread excellent in conductivity, heat conductivity and reinforcement. SOLUTION: Lc 20 to 40 °, oxygen content 10 to 50
A rubber filler for tire molding, comprising acetylene black of 0 μg / m ² . A bladder for vulcanizing a tire, comprising a bag-like molded product containing butyl rubber, a crosslinking agent for butyl rubber, a crosslinking accelerator, and a reinforcing material, wherein the reinforcing material is the above rubber filler. A tire tread comprising styrene butadiene rubber and / or natural rubber filled with silica powder and the above rubber filler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filler for tire molding and its use, and more particularly to a bladder for tire vulcanization and a tire tread.

[0002]

2. Description of the Related Art A tire vulcanizing bladder (hereinafter simply referred to as a "bladder") is used in a tire manufacturing process when an unvulcanized rubber to be a tire is put into a mold and vulcanized and molded. A non-vulcanized rubber is pressed into a mold by introducing high-pressure steam or high-temperature gas into the molded body, and heat is transferred through the molded body. Vulcanized.

Unvulcanized rubber has a low temperature rise due to poor thermal conductivity, and the time required for vulcanization molding is 15 to 20 minutes for passenger car tires and 45 to 60 minutes for large tires such as trucks.
Is said to be a minute. Therefore, the properties required for the bladder include high thermal conductivity, airtightness to the extent that high-pressure steam does not escape, and durability against repeated use.

[0004] From such a viewpoint, the conventional bladder is
Using butyl rubber with low gas permeability as a matrix,
A phenolic resin is used as a crosslinking agent for butyl rubber, and a halogen element-containing polymer such as chloroprene rubber, halogenated butyl rubber, or brominated butyl rubber is used as a vulcanization accelerator. As a reinforcing material, furnace black for rubber such as HAF, ISAF, or SAF is used. Further, it has been proposed to further use the acetylene black in combination with acetylene black in order to enhance the thermal conductivity (JP-A-9-29749).

However, this bladder has the following problems. Furnace black is a functional group containing oxygen (CO-, COOH) due to incomplete combustion of air such as heavy oil.
-, OH-, etc.), which add reinforcement to the rubber, thus improving the durability of the bladder filled with it, but having insufficient thermal conductivity, which reduces the vulcanization time. Reduction cannot be achieved sufficiently. In contrast, acetylene black has a high thermal conductivity, so this problem is small, but acetylene black is generated by self-heating decomposition of acetylene, so oxygen is not interposed, the surface functional groups are extremely small, and there is almost no reinforcing property. . Therefore, even when such acetylene black and furnace black are mixed, the thermal conductivity and durability of the bladder have not been sufficiently improved, and improvements have been awaited.

[0006] On the other hand, a tire tread is known in which styrene-butadiene rubber and / or natural rubber is used as a matrix and furnace black for rubber and silica powder are filled as reinforcing materials. The reason for using both of them is that by filling the silica powder, the rolling resistance can be reduced, but on the other hand, the conductivity of the tire is reduced, so static electricity is charged during running and discomfort to passengers when getting on and off It has been used in combination with furnace black for rubber to prevent such inconveniences as to cause inconvenience, to impair electronic components in the vehicle, and to cause ignition due to sparks during refueling. However, in the furnace black for rubber, since the conductivity is not high, this inconvenience cannot be sufficiently solved, and it is conceivable to change the furnace black to acetylene black.However, in general acetylene black, as described above, Reinforcement is reduced.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bladder and a tire tread excellent in all of conductivity, heat conductivity and reinforcement. The present inventors have conducted various studies to achieve this object, and as a result, have found that there is acetylene black having conductivity, heat conductivity, and reinforcing properties suitable as a rubber filler for tire molding, and completed the present invention. It was made.

[0008]

That is, according to the present invention, there is provided L
A rubber filler for tire molding, comprising acetylene black having a c of 20 to 40 ° and an oxygen content of 10 to 500 μg / m ² . Also, the present invention provides a butyl rubber,
A bladder comprising a bag-shaped molded article containing a butyl rubber crosslinking agent, a crosslinking accelerator and a reinforcing material, wherein the reinforcing material contains the rubber filler. Further, the present invention is a tire tread comprising a molded product in which styrene-butadiene rubber and / or natural rubber is filled with silica powder and the above rubber filler.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The acetylene black used in the present invention has a Lc (graphite layer thickness) of 20 to 40 ° and an oxygen content of 1%.
0 to 500 μg / m ² .

Acetylene black having an Lc of less than 20 ° has the same crystallinity as furnace black.
Even if a bladder or a tread tire is molded using this, there is no improvement in the thermal conductivity. Further, acetylene black having an Lc of more than 40 ° is difficult to impart a functional group containing oxygen to the surface of acetylene black due to the development of crystals, so that the thermal conductivity of the rubber molded body is improved.
Reinforcement decreases.

On the other hand, if the oxygen content of acetylene black is less than 10 μg / m ² , a sufficient reinforcing effect of the rubber molded article cannot be obtained, and if it is more than 500 μg / m ² , the functional group containing oxygen cannot be used. , Π on the carbon surface
Since the movement of electrons is hindered, the effect of improving the conductivity of the rubber molded article cannot be expected.

The particle size of acetylene black may be a fine powder in the form of a press used in a manganese dry battery, but it is preferable that the acetylene black is granulated to about 0.1 to 2 mm. For granulation, ion exchange water is often used as a wetting agent,
For details, see Japanese Patent Publication No. 1-58227,
No. 55892.

The acetylene black used in the present invention is obtained by an incomplete combustion method of acetylene gas (Japanese Patent No. 17854).
No. 82) or 500 ° C. of acetylene black
It can be manufactured by the air oxidation method described above (see Japanese Patent Application Laid-Open No. 62-187692).

The rubber filled with the acetylene black according to the present invention includes natural rubber, styrene butadiene rubber, acrylonitrile butadiene rubber and hydrogenated rubber thereof,
Butyl rubber, acrylic rubber, ethylene propylene rubber,
Ethylene propylene terpolymer, copolymer rubber of ethylene and α-olefin, ethylene acrylate copolymer rubber, thermoplastic elastomer such as silicone rubber, fluoro rubber, polyester, chloroprene rubber, polybutadiene, hydrin rubber, chlorosulfonated polyethylene, etc. is there. Of these, butyl rubber is used for bladder applications, and styrene butadiene rubber and / or natural rubber is used for tread applications.

When the rubber molded product is used as a bladder, it is not necessary to fill silica powder, but in the case of a tread, 100 parts (parts by mass; hereinafter the same) of rubber are used.
About 0 to 60 parts are filled. The shape of the silica powder may be spherical, non-spherical, crushed, or square-shaped, and a particle having an average particle size of 0.1 to 1 μm is generally used.

One example of the composition is as follows. In a bladder, 5 to 15 parts of a butyl rubber crosslinking agent are added to 100 parts of the butyl rubber.
Parts, 3-8 parts of a crosslinking accelerator, 40-6 acetylene black
0 parts. In the tread, a crosslinking agent is used in an amount of 3 to 3 parts per 100 parts of styrene-butadiene rubber and / or natural rubber.
5 parts, 3 to 7 parts of silane coupling agent, silica powder 2
0 to 60 parts, and 5 to 15 parts of acetylene black.

The molding of the bladder is performed as follows. First, the kneaded material is formed into a hollow circular shape by an extruder, or a hemispherical shape by pressing, and a valve serving as a steam or gas intake is attached.If the hollow circular shape is used, the two cuts are joined to form a ring. In the case of a hemispherical shape to be molded, both are joined to form a middle bag. Next, these are put into a mold and vulcanized through compressed air or steam inside and steam outside.

[0019]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1 and 2 Comparative Examples 1 to 3 A rubber molded product was produced according to the bladder specification. That is, carbon blacks shown in Table 1 (Examples 1 and 2 and Comparative Examples 1 and 2 were acetylene black, Comparative Example 3 was furnace black) were mixed with each material, and vulcanized to produce a rubber sheet. The thermal conductivity, volume resistivity, and vulcanization properties of the obtained rubber sheet were measured in the following manner.
Table 1 shows the results.

(1) Thermal conductivity Specific heat, density and thermal diffusivity were measured according to
The thermal conductivity was calculated by the following equation: thermal conductivity = specific heat × density × thermal diffusivity. <Specific heat> DSC scanning method (Seiko Electronics DSC200).
Sample weight: 30 mg, standard sample: α-Al2O3 (30
mg) Measurement temperature: 300K <Density> Archimedes method (underwater weight method). Density = dry mass / (dry mass-mass in water) <Thermal diffusivity> Laser flash method ("LF" manufactured by Rigaku Corporation)
/ TCM FA8510B ").

(2) Volume resistivity A sample of 20 mm × 100 mm × 2 mm was cut out from a rubber sheet and measured according to SRIS2301. (3) Vulcanization properties According to JIS K 6301, modulus (M200,
M400), TB (breaking strength) and EB (elongation) were measured.

The Lc and oxygen content of carbon black were measured as follows. (4) From the diffraction line on the (002) plane in the X-ray diffraction method using Lc Cu-Kα ray, the following equation is obtained: Lc (Å) = (180 · K · λ) /
(Π · β · COSθ). Where K = shape factor 0.9, λ = wavelength of X-ray (1.54 °), θ =
(002) The angle indicating the maximum value in the diffraction line absorption band, and β = the half-value width in the (002) diffraction line absorption band is indicated by the angle.

(5) Oxygen content After drying the carbon black at 250 ° C. for 20 hours, LEC
It measured using O company oxygen analyzer "TC-136".
The oxygen content measured by this measurement is derived from oxygen other than the adsorbed moisture, and is based on the metal oxide and the functional group containing oxygen in acetylene black. Since the amount of the metal oxide in acetylene black is contained in the acetylene gas and shows a substantially constant value, the difference in the oxygen content in this example and the comparative example is due to the difference in the number of functional groups containing oxygen. You can see.

[0025]

[Table 1]

From Table 1, it can be seen that the rubber sheets produced in Examples 1 and 2 were superior to Comparative Examples 1 to 3 in electrical conductivity, thermal conductivity and reinforcement. Therefore, the ladder made of this rubber sheet does not shorten the life of the bladder,
It can be seen that the vulcanization time can be reduced.

Examples 3 and 4 Comparative Examples 4 to 6 Rubber moldings were manufactured with tread specifications. That is, carbon blacks shown in Table 2 (Examples 3 and 4 and Comparative Examples 4 and 5 were acetylene black, Comparative Example 6 was furnace black) were mixed with each material, and vulcanized to produce a rubber sheet. The resulting sheet was measured for thermal conductivity, volume resistivity, and vulcanization properties. Table 2 shows the results.

[0028]

[Table 2]

From Table 2, it can be seen that the rubber sheets manufactured in Examples 3 and 4 were superior in conductivity, heat conductivity and reinforcement as compared with Comparative Examples 4 to 6. Therefore, it can be seen that the tire tread constituted by this rubber sheet becomes a silica-containing tire tread excellent in static electricity elimination.

[0030]

According to the present invention, a bladder and a tire tread excellent in conductivity, heat conductivity and reinforcement are provided.

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Claims (3)

[Claims] 1. Lc 20-40 °, oxygen content 10-5
A rubber filler for tire molding, comprising acetylene black of 00 μg / m ² . 2. A tire vulcanizer comprising a butyl rubber, a butyl rubber cross-linking agent, a cross-linking accelerator and a bag-like molded product containing a reinforcing material, wherein the reinforcing material contains the rubber filler according to claim 1. Bladder. 3. A tire tread comprising a molded product in which styrene-butadiene rubber and / or natural rubber is filled with silica powder and the rubber filler according to claim 1.