JP2002241544A - Rubber composition for side wall and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for side wall capable of improving visibility and appearance while securing crack resistance. SOLUTION: This rubber composition is obtained by compounding a rubber base with a white filler, a pigment and mica small pieces. The amount of the mica small piece compounded is 2-45 pts.wt. based on 100 pts.wt. of the rubber base.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a side wall which is suitable as a white rubber for forming a white letter and which can improve the appearance of the white letter while ensuring crack resistance, and a rubber composition for the same. The present invention relates to a pneumatic tire using the same.

[0002]

2. Description of the Related Art In recent years, as shown in FIG. 3 (A), a so-called white letter tire t which has a raised embossing mark m made of white rubber gc on the surface of a sidewall portion ts to enhance the decorative effect has been developed. Has appeared. This embossed mark m is
As schematically shown in FIG. 3 (B), a raised portion a for forming a raised mark raised by vulcanization molding is buffed and a thin black covering rubber layer ga covering the surface is removed. The white rubber gc embedded in the sidewall rubber gb is exposed.

[0003] By the way, rubber used for tires includes:
Usually, to improve ozone resistance, crack resistance, etc.
It contains compounding agents such as anti-aging agents and waxes (fatty acids). However, when the compounding agent is used for white rubber, there is a problem that the rubber itself is contaminated, discolored in brown, and the appearance appearance is significantly impaired.

Therefore, white rubber gc usually has excellent weather resistance, for example, butyl rubber (IIR), halogenated butyl rubber (X-IIR), ethylene-propylene rubber (E).
By using an olefin rubber such as FDM), suppression of the discoloration is achieved. In order to increase the whiteness of the rubber, white pigments such as titanium oxide and zinc white are used in addition to white fillers such as silica and clay.

[0005]

However, the use of only such conventional white fillers and white pigments merely gives a white color and cannot provide brightness, so that the decorative effect by the embossed marks cannot be obtained. It was difficult to sufficiently pull it out, and the visibility and appearance were poor.

The present invention is based on the fact that a predetermined amount of mica particles having an excellent light reflection ability and a metallic luster is mixed with the white rubber, while ensuring the crack resistance required for the side wall rubber. Another object of the present invention is to provide a rubber composition for a sidewall, which can give a white metallic luster and improve visibility and appearance, and a pneumatic tire using the same.

[0007]

Means for Solving the Problems In order to achieve the above object, claim 1 of the present application is an invention of a rubber composition for a side wall, wherein a white filler, a pigment and mica particles are added to a rubber substrate. Rubber base 1
The amount is 2 to 45 parts by weight with respect to 00 parts by weight, and the mica particles have an average particle size of 10 to 300 μm.

A second aspect of the present invention relates to a pneumatic tire, wherein the rubber composition for a sidewall according to the first aspect is used as a white rubber for a white letter.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described.
This will be described together with the illustrated example. FIG. 1 shows that the rubber composition W for a side wall of the present invention comprises a white rubber G for a white letter.
It is sectional drawing which shows the pneumatic tire 1 when used as c.

In FIG. 1, a pneumatic tire 1 has a tread portion 2, a sidewall portion 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 located at an inner end of each sidewall portion 3. And a raised mark 9 made of white rubber Gc is formed on the surface of the side wall portion 3.

Reference numeral 6 in FIG. 1 denotes a carcass straddling between the bead portions 4 and 4, and reference numeral 7 denotes a belt layer disposed outside the carcass 7 and inside the tread portion 2.

The carcass 6 is formed from at least one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 70 to 90 degrees with respect to the tire circumferential direction, in this embodiment, one carcass ply 6A. The carcass ply 6 </ b> A is locked by bending both ends around the bead core 5 of the bead portion 4.

The belt layer 7 is formed of a high-strength belt cord such as a steel cord in the circumferential direction of the tire.
It is formed from at least two belt plies 7A and 7B in this example arranged at an angle of 0 to 35 degrees. The belt plies 7A and 7B are arranged in different inclination directions so that the belt cords intersect between the plies, whereby the substantially entire width of the tread portion 2 is reinforced with a strong tagging effect. .

Next, the sidewall rubber 3G forming the sidewall portion 3 is a black main sidewall rubber G.
b, a white rubber Gc for forming a white letter embedded therein, and a thin black coating rubber layer Ga covering the surface of the white rubber Gc.

As shown in FIG. 2, the raised mark 9 is buffed with a raised portion A for forming a raised mark formed by vulcanization molding as in the prior art. By removing the rubber layer Ga, the white rubber Gc inside is exposed and formed.

In this embodiment, the white rubber Gc
The rubber composition W for a side wall containing mica particles (hereinafter sometimes simply referred to as a rubber composition W) is used.

This rubber composition W is obtained by mixing a white filler, a pigment and mica particles with a rubber substrate, and the compounding amount of the mica particles is 2 to 45 parts by weight based on 100 parts by weight of the rubber substrate. Department.

Here, as the rubber substrate, for example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR)
A diene rubber such as butyl rubber (IIR), halogenated butyl rubber X-IIR) having excellent weather resistance, an olefin rubber such as ethylene propylene rubber (EFDM), and a mixture of the diene rubber and the olefin rubber. Can be used.

In particular, for the purpose of eliminating or restricting the use of compounding agents such as antioxidants and waxes as a rubber base material and preventing contamination (brown discoloration) by the compounding agent, the olefin rubber or the olefin rubber is used. It is preferable to use a blend rubber of a rubber and a diene rubber. In the case of a blended rubber, the olefin rubber is added to a rubber base material in an amount of 20%.
It is preferable that the content be at least part by weight in order to impart sufficient weather resistance.

However, in the present invention, the contamination (brown discoloration) due to an antioxidant or the like can be concealed to some extent by improving the appearance of the mica particles. Therefore,
Regulations on the use of an antioxidant and the like can be relaxed to some extent, and the rubber base material can be constituted only by diene rubber.

The white filler replaces a black filler such as carbon black to reinforce the rubber and improve rubber properties such as tensile strength and hardness. For example, silica known as white carbon, Examples include inorganic fillers such as magnesium silicate, calcium carbonate, magnesium carbonate, clay, and talc. These white fillers can be used alone or in combination of two or more, and it is preferable that at least silica is contained from the viewpoint of a reinforcing effect.

The amount of the white filler is not particularly restricted because it is appropriately set in accordance with the rubber properties of the main sidewall rubber Gb, but is usually 20 to 90 parts by weight based on 100 parts by weight of the rubber base material. The range of parts is common.

Next, in the rubber composition W, a white pigment is blended in order to color the rubber into a predetermined color, in this example, white. Examples of the white pigment include titanium oxide and zinc white, and these can be used alone or as a mixture of two or more. However, it is preferable to include at least the titanium oxide having the best hiding power in order to improve whiteness.

The pigment may be, for example, a red pigment (such as redwood or cadmium red) depending on the color to be colored in addition to white.
Yellow pigment (titanium yellow, orange lake, etc.), green pigment (phthalocyanine green, etc.), blue pigment (ultramarine, etc.)
And the like, or a mixture of colored pigments, or a mixture of colored and white pigments. Also, the compounding amount is appropriately set according to the color to be colored and the type of pigment, and thus is not particularly limited in the present application. However, for example, when forming the white rubber Gc, the white pigment is added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the rubber base material.
It is preferred to mix in parts by weight.

The mica particles are in the form of platelets having an average particle size of 10 to 300 μm obtained by finely pulverizing mica. For example, when extruding a white rubber Gc using an extruder or a calendar machine, it is caused by rubber flow. The mica particles have a property of being oriented substantially parallel to the surface of the white rubber Gc.

As is well known, mica is a mineral having the property of being able to be peeled off evenly and thinly, and its surface is excellent in light reflection effect and has metallic luster.
Further, there is a feature that there is no discoloration and the light reflection effect is stably exhibited for a long period of time.

Therefore, the white rubber G
When c is exposed, the surface side of the mica particles to be oriented easily peels off thinly, and a clean surface (peeled surface) on which rubber or the like is not adhered can be exposed on the surface of the embossed mark 9.

As a result, the light reflecting effect of the mica particles is sufficiently exhibited, and the surface of the embossing mark 9 exhibits a glittering metallic luster, so that the sharpness and brightness in addition to the whiteness are enhanced. Visibility and appearance are improved.

In addition, the mica particles have a white rubber Gc mixed with, for example, an antioxidant, and even when contamination (brown discoloration) occurs over time, the discoloration is concealed by imparting metallic luster. The appearance can be improved.

On the other hand, white rubber Gc (rubber composition W)
Since it is used for the side wall portion 3, it is important to ensure sufficient crack resistance. For this reason, in the present embodiment, the amount of the mica particles is limited to a range of 2 to 45 parts by weight based on 100 parts by weight of the rubber base material. If the amount is less than 2 parts by weight, the effect of improving the appearance cannot be achieved, while if it exceeds 45 parts by weight, crack resistance is impaired and durability of the tire is significantly reduced. Therefore, the amount of the mica particles is preferably in the range of 5 to 35.

It is also necessary that the mica particles have an improved appearance as much as possible with a limited blending amount. For this reason, in this example, the average particle size of the mica particles is 10 to 300 μm.
m. If the average particle size is less than 10 μm, the surface area (reflection area) of each mica piece becomes too small and the orientation during extrusion molding is poor, so that the light reflection effect is reduced and the appearance is improved. On the other hand, if it exceeds 300 μm, the mica particles are too large and come off from the rubber surface, which leads to a decrease in the appearance and a tendency to deteriorate the crack resistance. Therefore, the average particle size is more preferably in the range of 20 to 250 μm.

There are various types of mica, for example, muscovite, phlogopite, biotite, and these can be used alone or in combination of two or more. However, in the case of white rubber Gc as in this example, it is preferable to use muscovite from the viewpoint of appearance.

If necessary, a known vulcanizing agent, vulcanization accelerator, vulcanization accelerator, plasticizer, and silane coupling agent may be added to the white rubber Gc (rubber composition W). Various additives generally used for tires, such as antioxidants and waxes, can be added.

The main sidewall rubber Gb and the covering rubber layer G, which constitute the remainder of the sidewall rubber 3G,
a is a black diene rubber using the same carbon black as the conventional filler, and has ozone resistance,
An antioxidant, a wax or the like is blended for improving crack resistance and the like. In addition, it goes without saying that a vulcanizing agent, a vulcanization accelerator, a vulcanization acceleration aid, a plasticizer and the like may be added to these.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, but may be implemented in various forms.

[0036]

EXAMPLES White letter tires having raised marks formed using white rubber having the specifications shown in Table 1 were prototyped, and the appearance performance of each test tire, crack resistance and crack growth resistance of the white rubber were tested. .

(1) Appearance performance: The tire of the conventional example (without mica small pieces) was evaluated by visual evaluation according to a five-point scale of three. The higher the value, the better.

(2) Crack resistance; JISK6260
The crack growth was tested using a DeMatcher flex crack tester according to the flex crack test described in the above. In the test, a prescribed crack was applied to a test piece obtained by vulcanizing white rubber, and the number of flexing times required for the crack to grow 1 mm was measured. The upper limit was 990,000 bending cycles, and ○ indicates that no growth occurred even after 990,000 times, and x indicates that growth did not occur.

[0039]

[Table 1]

As shown in the table, it can be confirmed that the tires of the examples can improve the appearance while maintaining the crack resistance.

[0041]

As described above, according to the present invention, a predetermined amount of mica particles having excellent light reflection ability and metallic luster are blended in the colored rubber, so that the crack resistance required for the side wall rubber is reduced. It is possible to give a metallic bright shine while securing, and it is possible to improve visibility and appearance.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a side wall portion.

FIGS. 3A and 3B are diagrams illustrating a problem of the related art.

[Explanation of symbols]

 3 Sidewall part W Sidewall rubber composition

Claims (2)

[Claims] 1. A rubber base material comprising a white filler, a pigment and mica particles mixed therein, and the amount of the mica particles added to the rubber substrate 1
The rubber composition for a side wall, wherein the mica particles have an average particle size of 10 to 300 μm, in addition to 2 to 45 parts by weight based on 00 parts by weight. 2. A pneumatic tire, wherein the rubber composition for a sidewall according to claim 1 is used for a white letter arranged on a sidewall portion of the tire.