JP2001316521A - Rubber composition and pneumatic tire produced by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition having improved heat-resistance and usable as a bead filler and/or a side wall reinforcing layer of a tire and provide a pneumatic tire produced by using the composition. SOLUTION: The rubber composition for a bead filler and/or a side wall reinforcing layer of a tire contains (A) natural rubber and/or a synthetic diene rubber and (B) an acrylate. The pneumatic tire contains the rubber composition in the rubber reinforcing layer of a side wall and/or the bead filler of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition and a pneumatic tire using the same. For more information,
The present invention provides a rubber composition having improved heat resistance and used as a bead filler and / or a sidewall reinforcing layer of a tire, and a pneumatic composition obtained by using the rubber composition for a sidewall reinforcing layer and a bead filler. It is about tires.

[0002]

2. Description of the Related Art Conventionally, in a tire, a side reinforcing layer made of a rubber composition alone or a composite of a rubber composition and fibers is provided in order to improve the rigidity of a sidewall portion. However, in the conventional rubber compositions used for these, in particular, as in so-called run-flat running, the vehicle travels in a state where the internal pressure of the tire (hereinafter, referred to as internal pressure) is reduced due to puncture of the tire. In addition, when the temperature is 200 ° C. or higher, a crosslinked portion formed by vulcanization or the like, or a polymer itself constituting a rubber component, tends to be cut. Due to this, since the elastic modulus decreases, the deflection of the tire increases, heat generation proceeds, and the breaking limit of rubber decreases, as a result,
Tires have a problem that they break down relatively early.
As one of means for delaying the occurrence of such a failure as much as possible, by changing the compounding, the elastic modulus of the rubber composition to be used is increased as much as possible, or its loss tangent (tan δ) is set as small as possible. Although a method of suppressing heat generation of the rubber composition itself is known, there is a limit in an approach from a compounding side, and in run-flat running, a side reinforcing layer and a bead filler are required to secure a certain durable distance. As a result, during normal driving, undesired situations such as deterioration of ride comfort, deterioration of noise level, and increase in weight are caused.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a rubber composition having improved heat resistance used as a bead filler and / or a side wall reinforcing layer of a tire under such circumstances, and this rubber composition. It is an object of the present invention to provide a pneumatic tire using a material, particularly having excellent durability in run flat running.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, a rubber composition containing a specific compound has excellent heat resistance, and has a bead filler and / or It can be suitably used for the sidewall part reinforcing layer, and the pneumatic tire using this rubber composition for the sidewall part reinforcing layer and the bead filler has excellent durability especially in run flat running. I found it. The present invention has been completed based on such findings. That is, the present invention provides a rubber composition for a tire bead filler and / or a side wall portion reinforcing layer, comprising (A) a natural rubber and / or a diene-based synthetic rubber, and (B) an acrylate. To provide. The present invention also provides a pair of left and right ring-shaped bead cores, a bead filler disposed radially outside the bead core, and at least one ply in which a plurality of parallel cords are embedded in the covering rubber. A carcass layer, a belt layer disposed radially outside of the carcass layer, a tread portion disposed radially outside of the belt layer, and a pair of tread portions disposed on the left and right of the tread portion. In a pneumatic tire comprising a side wall portion and a rubber reinforcing layer provided on the side wall portion, the rubber reinforcing layer provided on the side wall portion and / or the bead filler may be provided with the rubber A pneumatic tire using the composition is also provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the rubber composition of the present invention,
As the component (A), a natural rubber and / or a diene-based synthetic rubber is used. Here, as the diene-based synthetic rubber,
For example, polyisoprene synthetic rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SB
R), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like. The natural rubber and the diene-based synthetic rubber of the component (A) may be used alone or in combination of two or more. Further, the reinforcing filler used in the rubber composition of the present invention is not particularly limited, and those usually used in the rubber industry can be appropriately selected, but preferably include carbon black, silica, aluminum hydroxide and the like. When silica or aluminum hydroxide is used, the use of the coupling agent together with the coupling agent can further enhance the reinforcing property with rubber. In the rubber composition of the present invention, acrylates are used as a heat aging inhibitor of the component (B) in order to improve heat resistance. In the present invention, as the acrylates, from the viewpoint of effects,
Polyesters of polyhydric alcohols with acrylic acid or acrylic acid and other carboxylic acids are preferred.

[0006]

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Compounds represented by the following formulas can be preferably mentioned. In the general formula (I), A represents a residue excluding a hydroxyl group of a (p + q) -valent polyhydric alcohol, and R represents a hydrogen atom or an acyl group other than an acryloyl group. The acyl group is not particularly limited, but is preferably a saturated or unsaturated aliphatic acyl group having 2 to 20 carbon atoms. p represents an integer of 2 to 10 and q represents an integer of 0 to 8, where p + q = 2 to 10. Among the compounds represented by the general formula (I), those in which p is an integer of 3 to 6 and q is an integer of 0 to 3 and p + q = 3 to 6 are preferable in terms of effect. General formula (II) A- (OH) _{p + q} ... (II) used for forming the acrylate represented by the general formula (I) (wherein A and p, q are the same as described above) )), Tri- to hexa-hydric alcohols are preferred, such as glycerin,
Trimethylolethane, trimethylolpropane, diglycerin, pentaerythritol, dipentaerythritol, sorbitol and the like. As the compound represented by the general formula (I), from the viewpoint of effects, a polyvalent ester of dipentaerythritol having 3 to 6 acryloyl groups in one molecule and acrylic acid and an acryloyl group 3 in one molecule Acyl group-modified dipentaerythritol acrylates having up to 5 are preferred. Such compounds are commercially available as shown below. For example, the expression

[0008]

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(A compound of a = 5, b = 1 and a = 6, b =
0) is a compound represented by “KAY
ARAD DPHA "(trademark, manufactured by Nippon Kayaku Co., Ltd.)

[0010]

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(R ¹ is Alkynoyl
l) represents a group. ) Is c = 5, d = 1
In the case of KAYAARD D-310 (trademark, manufactured by Nippon Kayaku Co., Ltd.), and in the case of c = 3, d = 3,
RAD D-330 "(trademark, manufactured by Nippon Kayaku Co., Ltd.). The acrylate of the component (B) exhibits the effect of improving the heat resistance of the rubber composition, but its action reacts with the conjugate C = C in the main chain generated at the time of crosslinking cleavage at a high temperature, This is considered to be due to the effective formation of C crosslinks.

In the present invention, as the component (B), the above acrylates may be used alone or in combination of two or more. In addition, the compounding amount is as described in the above (A)
0.5 parts by weight per 100 parts by weight of the rubber component
It is selected in the range of ２０20 parts by weight. If the amount is less than 0.5 parts by weight, the effect of preventing heat aging cannot be sufficiently obtained, and the desired effect of improving heat resistance may not be exhibited. Meanwhile, 2
If the amount is more than 0 parts by weight, the effect is not so much improved for the amount, and it is economically disadvantageous and causes other physical properties of the obtained rubber composition to deteriorate. In consideration of the effect of preventing heat aging, other physical properties and economics of the rubber composition, the more preferable amount of the component (B) is 1.0.
-15 parts by weight. In the present invention, if desired, other heat aging inhibitors, for example, sodium 1,6-hexamethylenedithiosulfate dihydrate, can be used in combination with the compound of the component (B). This sodium 1,6-hexamethylene dithiosulfate dihydrate has an action of suppressing the cross-linkage between polymer molecules constituting the rubber component.

The rubber composition of the present invention contains, in addition to the above components, vulcanizing agents usually used in the rubber industry, such as sulfur and peroxide, vulcanization accelerators, antioxidants, softeners and inorganic materials. Various compounding agents such as a filler can be appropriately contained. Further, the rubber composition of the present invention further includes particles of various materials,
It may be a composite with fiber, cloth and the like. To produce the rubber composition of the present invention, the maximum temperature in the step of kneading the acrylate (B) component is preferably 140 ° C. or less,
More preferably, the temperature is adjusted to 120 ° C. or lower. In the kneading step, a vulcanizing agent or the like may be added for kneading, or only the component (B) may be separately kneaded. The rubber composition of the present invention has excellent heat resistance and is used as a bead filler and / or a sidewall part reinforcing layer of a tire.

The heat resistance of the rubber composition of the present invention can be evaluated as follows. That is, the dynamic storage elastic modulus of a sample of the vulcanized rubber composition is measured under elevated temperature conditions, and the change in the dynamic storage elastic modulus with respect to temperature is represented by a graph. From this graph, the value of the peak dynamic storage modulus and its temperature, the value of the bottom dynamic storage modulus and its temperature,
Further, the dynamic storage modulus at 250 ° C. is determined. Then, the bottom dynamic storage modulus / peak dynamic storage modulus is calculated from the above values. The larger the value, the larger the value of the dynamic storage modulus at 250 ° C., the better the heat resistance.

Next, with respect to the pneumatic tire of the present invention,
This will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of an example of the pneumatic tire of the present invention. The pneumatic tire 1 is disposed on a pair of left and right ring-shaped bead cores 4 and radially outside the bead cores 4 in the tire radial direction. A bead filler 5 and a carcass layer 2 composed of at least one ply in which a plurality of parallel cords are embedded in a covering rubber.
A belt layer 3 disposed radially outward of the carcass layer 2 in the tire radial direction; a tread portion 8 disposed radially outward of the belt layer 3 in the tire radial direction; And a rubber reinforcing layer 7 provided on the side wall portion 6. The carcass layer 2 has a folded carcass ply 2a and a down carcass ply 2b, and both ends of the folded carcass ply 2a are folded around the bead core 4 to form folded ends. The bead filler 5 is located between the folded carcass ply 2a and its folded end, and the down carcass ply 2b is arranged between the sidewall portion 6 and the folded end of the folded carcass ply 2a. ing. The rubber reinforcing layer 7 is arranged in a crescent cross section on the inner peripheral surface of the sidewall portion of the folded carcass ply 2a. In the pneumatic tire of the present invention, the above-described bead filler 5 and / or the rubber reinforcing layer 7 are formed using the above-described rubber composition of the present invention.

The rubber composition of the present invention has a rubber composition temperature of 170 due to large deformation due to puncture of a tire or the like.
Since the decrease in the modulus of elasticity is suppressed even at a temperature of not less than ° C, heat generation at high temperatures is suppressed, and the durability of the tire can be improved. Therefore, the pneumatic tire of the present invention using this rubber composition for the bead core or the rubber reinforcing layer of the side wall portion has a significantly improved durability, particularly in run flat running, and can significantly extend the running distance. .

[0017]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The properties of the obtained rubber composition and the run flat durability of the tire were determined according to the following procedures. (1) Dynamic storage elastic modulus (E ′) of rubber composition From a 2 mm thick slab sheet obtained by vulcanizing a rubber composition at 160 ° C. for 12 minutes, a width of 5 mm and a length of 4
A sheet of 0 mm was cut out and used as a sample. For this sample, using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd., a temperature in a range of 25 to 250 ° C. under measurement conditions of a distance between chucks of 10 mm, an initial strain of 200 micrometers (microns), a dynamic strain of 1%, and a frequency of 52 Hz. , The dynamic storage elastic modulus was measured at a rate of temperature rise of 3 ° C./min, and the change in the dynamic storage elastic modulus with respect to temperature is shown in a graph. From this graph, the value of the peak dynamic storage modulus and its temperature, the value of the bottom dynamic storage modulus and its temperature, and the dynamic storage modulus at 250 ° C. were determined. Storage modulus / peak dynamic storage modulus was calculated. Each of the above values was indicated as an index with Comparative Example 1 being 100. The larger the index of the bottom dynamic storage modulus / the peak dynamic storage modulus and the larger the index of the dynamic storage modulus at 250 ° C., the better the heat resistance. (2) Run-flat durability of the tire After assembling the rim at normal pressure and filling the internal pressure of 200 kPa,
After being left at room temperature of 8 ° C. for 24 hours, the core of the valve was removed, the internal pressure was set to atmospheric pressure, and a drum running test was performed under the conditions of a load of 5.6 kN (570 kg), a speed of 89 km / h, and a room temperature of 38 ° C. The running distance until the occurrence of a failure at this time was defined as run flat durability, and was represented by an index with Comparative Example 1 being 100. The larger the index, the better the run flat durability.

Examples 1-19 30.0 parts by weight of natural rubber and butadiene rubber "BR0"
1 "[trademark, manufactured by JSR Corporation] 60.0 parts by weight of carbon black FEF, 3.0 parts by weight of spindle oil, 5.0 parts by weight of zinc white per 100 parts by weight of a rubber component consisting of 70.0 parts by weight. 1.0 parts by weight of stearic acid and an antioxidant "Nocrack 6C" [trademark, N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.] 2.0 parts by weight were blended, and the maximum temperature was 170 ° C. and kneading was performed.
Next, the mixture obtained above was added to the vulcanization accelerator “Noxera-NS” [trademark, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Nt
tert-butyl-2-benzothiazolylsulfenamide] and 2.5 parts by weight of (B) of the kind and amount shown in Table 1.
The component compound and 6.0 parts by weight of sulfur were added, and the maximum temperature was 1
The mixture was kneaded at 00 ° C. to prepare a rubber composition. In addition,
The component compound (B) is silica (Nipsi) according to a conventional method.
lAQ, manufactured by Nippon Silica Industry Co., Ltd.) as a 50% by weight carrier. Table 1 shows the properties of the vulcanizate.

Next, a radial tire for passenger cars having a size of 225 / 60R16 is manufactured according to a conventional method by using the rubber composition for a bead filler and / or a side wall reinforcing layer (side reinforcing rubber). Flat durability was evaluated. The results are shown in Table 1. Comparative Example 1 The rubber compositions shown in Table 1 were prepared in the same manner as in Examples 1 to 19, except that the component compound (B) was not used. Various characteristics of this vulcanizate
It is shown in the table. Next, the above composition was applied to both the side wall portion reinforcing layer and the bead filler, and
A tire was manufactured in the same manner as in Example 9, and its run flat durability was evaluated. The results are shown in Table 1.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

(Note) 1) Component compound (B): Deterioration inhibitor A; "KAYARAD D310" (trademark)
Nippon Kayaku Co., Ltd.] Deterioration inhibitor B; “KAYARAD DPHA” [trademark,
Nippon Kayaku Co., Ltd.] Deterioration inhibitor C; "KAYARAD D330" [trademark,
Nippon Kayaku Co., Ltd.) 2) Applicable members: Each of the rubber compositions shown in Table 1 is applied. As is clear from Table 1, the component compound (B)
It is understood that the rubber composition blended at a ratio of 0.5 to 20 parts by weight with respect to 100 parts by weight of the rubber component has an improved effect of heat resistance. A pneumatic tire using this rubber composition for a bead filler or a sidewall reinforcing layer has good run flat durability, and particularly a tire using both the bead filler and the sidewall reinforcing layer. Has excellent run flat durability.

[0024]

According to the present invention, it is possible to obtain a rubber composition having improved heat resistance by using a specific compound, which is used for a bead filler and / or a sidewall reinforcing layer of a tire. Used as The pneumatic tire of the present invention using this rubber composition for the side wall portion reinforcing layer and the bead filler has excellent durability especially in run flat running, and can significantly extend the running distance.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of an example of a pneumatic tire according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire of the present invention 2 Carcass layer 2a Folded carcass ply 2b Down carcass ply 3 Belt layer 4 Bead core 5 Bead filler 6 Side wall part 7 Rubber reinforcing layer 8 Tread part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 9/00 C08L 9/00

Claims (10)

[Claims] 1. A rubber composition for a bead filler and / or sidewall reinforcing layer of a tire, comprising (A) a natural rubber and / or a diene-based synthetic rubber and (B) an acrylate. 2. The rubber composition according to claim 1, wherein the acrylate component (B) is a polyhydric ester of a polyhydric alcohol and acrylic acid or acrylic acid and another carboxylic acid. 3. The acrylate of the component (B) is represented by the general formula (I): (In the formula, A is a residue excluding a hydroxyl group of a (p + q) -valent polyhydric alcohol, R is a hydrogen atom or an acyl group other than an acryloyl group, p is an integer of 2 to 10, and q is an integer of 0 to 8. The rubber composition according to claim 2, which is a compound represented by the following formula: p + q = 2 to 10. 4. In the acrylate represented by the general formula (I) of the component (B), p is an integer of 3 to 6, and q is 0 to 0.
4. The rubber composition according to claim 3, wherein p is an integer of 3 and p + q = 3 to 6. 5. The acrylate represented by the general formula (I) as the component (B) is a polyvalent ester of dipentaerythritol having 3 to 6 acryloyl groups in one molecule and acrylic acid. 5. The rubber composition according to 4. 6. The rubber composition according to claim 4, wherein the acrylate represented by the general formula (I) as the component (B) is an acyl group-modified dipentaerythritol acrylate having 3 to 5 acryloyl groups in one molecule. object. 7. (B) per 100 parts by weight of component (A)
The rubber composition according to any one of claims 1 to 6, comprising 0.5 to 20 parts by weight of a component. 8. The rubber composition according to claim 1, wherein in the kneading step of dispersing the acrylate component (B) in the rubber, the rubber composition is kneaded at a maximum temperature of 140 ° C. or lower. 9. The rubber composition according to claim 1, which is kneaded at a maximum temperature of 120 ° C. or less in the kneading step of dispersing the acrylate (B) in the rubber. 10. A pair of left and right ring-shaped bead cores,
A bead filler disposed outside the bead core in the tire radial direction, a carcass layer composed of at least one ply in which a plurality of cords arranged in parallel are embedded in the covering rubber, and The disposed belt layer, a tread portion disposed outside the belt layer in the tire radial direction, a pair of sidewall portions disposed on the left and right sides of the tread portion, and a rubber disposed on the sidewall portion. In a pneumatic tire having a reinforcing layer, the rubber composition according to any one of claims 1 to 9 is used for the rubber reinforcing layer and / or the bead filler disposed on the sidewall portion. A pneumatic tire, characterized in that: