JP2011116815A - Rubber composition for tire and pneumatic tire obtained using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire that has a low-heat build-up property and is excellent in elongation at break, crack resistance and ozone resistance at an initial stage and after ageing, and a pneumatic tire using the same. <P>SOLUTION: The rubber composition for a tire includes 100 pts.mass of a diene rubber comprising a natural rubber and/or an isoprene rubber, and incorporated therewith, 15-70 pts.mass of carbon black having a nitrogen adsorption specific surface area (N<SB>2</SB>SA) of at least 30 m<SP>2</SP>/g and less than 80 m<SP>2</SP>/g and 0.5-10 pts.mass of a phenol derivative represented by formula 1 (wherein R<SP>1</SP>and R<SP>2</SP>are each independently a 6-12C alkyl group; and R<SP>3</SP>is a hydrogen atom or a 1-6C alkyl group). The pneumatic tire is obtained by using the rubber composition for a tire for a belt cushion (8), an upper bead filler (62) and a sidewall (2). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a tire rubber composition and a pneumatic tire using the same, and more particularly, to a tire rubber composition particularly suitable for use in tire belt cushions, upper bead fillers, and sidewalls, and to the same. It relates to the used pneumatic tire.

Since the tire belt cushion and the upper bead filler are disposed inside the tire, it is important that they easily accumulate heat and have low heat generation. In addition, since a large force is applied to the tire while it is deformed, it may cause a destructive phenomenon such as a crack or a separation, and sufficient consideration is required.
From this, it can be said that the tire belt cushion and the upper bead filler have important physical properties such as low exothermic property, initial and post-aging breaking elongation, and crack resistance.
In general, in order to maintain the elongation at break after aging, it is effective to use a vulcanization accelerator that produces a large amount of mono- and disulfide crosslinks, but the initial break elongation and crack resistance are reduced. End up. Moreover, adding an anti-aging agent is one means, but if an anti-aging agent used in a normal diene rubber composition is added, the heat build-up will deteriorate.

  On the other hand, since the sidewall of the tire is subjected to a large strain, it is required to increase the elongation at break in the initial stage and after aging. Further, since the sidewall is exposed to ozone during use of the tire, it is necessary to prevent the occurrence of cracks due to ozone degradation.

  In addition, although the phenol derivative used by this invention demonstrated below is a well-known compound (for example, refer patent document 1), the said phenol derivative is used as one component in the rubber composition for tires, low exothermic property, favorable The technical idea of obtaining elongation at break, crack resistance and ozone resistance is not disclosed or suggested in the prior art.

JP 2009-114160 A

  Accordingly, an object of the present invention is to provide a rubber composition for a tire which has low heat build-up and is excellent in break elongation, crack resistance and ozone resistance after initial and aging, and a pneumatic tire using the same. .

As a result of intensive research, the present inventors can solve the above-mentioned problems by blending a specific amount of carbon black having a specific property with a specific diene rubber and a specific amount of a specific phenol derivative. The present invention was completed.
That is, the present invention is as follows.
1. To natural rubber and / or diene rubber 100 parts by mass including isoprene rubber, a nitrogen adsorption specific surface area _(N 2 SA) of ^{30 m} 2 / g or more ^{80 m} 2 / g less than the carbon black from 15 to 70 parts by weight and the following formula A rubber composition for tires, comprising 0.5 to 10 parts by mass of the phenol derivative represented by 1.

[Chemical 1]

(In Formula 1, R ¹ and R ² each independently represents an alkyl group having 6 to 12 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms)
2. 2. The tire rubber composition as described in 1 above, wherein the proportion of natural rubber and / or isoprene rubber is 50 parts by mass or more in 100 parts by mass of the diene rubber.
3. 2. The rubber composition for tires according to 1 above, wherein the diene rubber further comprises butadiene rubber, and the proportion of the butadiene rubber is 50 to 80 parts by mass in 100 parts by mass of the diene rubber. .
4). A pneumatic tire using the tire rubber composition described in 2 above as a belt cushion.
5). A pneumatic tire using the tire rubber composition described in 2 above as an upper bead filler.
6). A pneumatic tire using the tire rubber composition described in 3 above as a sidewall.

  According to the present invention, a specific amount of carbon black having specific characteristics is blended with a specific diene rubber, and a specific phenol derivative is blended with a specific amount. A rubber composition for tires excellent in elongation at break, crack resistance and ozone resistance, and a pneumatic tire using the same can be provided.

It is a fragmentary sectional view of an example of a pneumatic tire.

  Hereinafter, the present invention will be described in more detail.

FIG. 1 is a partial cross-sectional view of an example of a pneumatic tire.
In FIG. 1, a pneumatic tire is composed of a pair of left and right bead portions 1 and sidewalls 2, and a tread 3 connected to both sidewalls 2, and a carcass layer 4 in which a steel cord is embedded between the bead portions 1 and 1 is mounted. Then, the end portion of the carcass layer 4 is turned up around the bead core 5 and the bead filler 6 from the tire inner side to the outer side. The bead filler 6 is composed of two members, the upper part being an upper bead filler 62 and the lower part being a lower bead filler 64. In the tread 3, a belt layer 7 is disposed over the circumference of the tire outside the carcass layer 4. Belt cushions 8 are disposed at both ends of the belt layer 7. An undertread 31 is disposed on the inner peripheral side of the tread 3. An inner liner 9 is provided on the inner surface of the pneumatic tire to prevent the air filled inside the tire from leaking to the outside of the tire, and a tie rubber 10 for bonding the inner liner 9 is attached to the carcass layer 4. It is laminated between the inner liner 9.

  The rubber composition of the present invention is particularly useful for forming the sidewall 2, the belt cushion 8, and the upper bead filler 62. Next, each component of the rubber composition of the present invention will be described.

(Diene rubber)
The diene rubber component used in the present invention contains natural rubber (NR) and / or isoprene rubber (IR). The diene rubber component used in the present invention may contain a rubber component other than those described above. Examples thereof include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and the like. 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.
In the diene rubber component, when the ratio of NR and / or IR is 50 parts by mass or more, more preferably 80 parts by mass or more, the exothermic property, the initial and post-aging elongation at break, and the crack resistance are good. From the viewpoint of becoming, it is particularly useful for forming the belt cushion 8 and the upper bead filler 62.
The diene rubber component further contains BR in addition to NR and / or IR, and the proportion of the BR in the diene rubber 100 parts by mass is 50 to 80 parts by mass, more preferably 60 to 80 parts by mass. Is particularly useful for the formation of the sidewall 2 from the viewpoints of exothermic property, initial and post-aging elongation at break, and ozone resistance.

(Carbon black)
The carbon black used in the present invention needs to have a nitrogen adsorption specific surface area (N ₂ SA) of 30 m ² / g or more and less than 80 m ² / g. If the nitrogen adsorption specific surface area (N ₂ SA) is less than 30 m ² / g, the rigidity is insufficient and is not preferable. Conversely, if it is 80 m ² / g or more, the exothermic property is deteriorated. The nitrogen adsorption specific surface area (N ₂ SA) is a value determined in accordance with JIS K6217-2.

(Phenol derivative)
The phenol derivative used in the present invention is represented by the following formula 1.

[Chemical 2]

(In Formula 1, R ¹ and R ² each independently represents an alkyl group having 6 to 12 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms)

As described above, in Formula 1, R ¹ and R ² each independently represents an alkyl group having 6 to 12 carbon atoms, preferably an alkyl group having 7 to 11 carbon atoms, It may be branched. Examples of such an alkyl group include a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group, and among them, a heptyl group, an octyl group, a nonyl group, a decyl group, and an undecyl group are preferable. .
R ³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, and may be linear or branched. Examples of such an alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Of these, a hydrogen atom, a methyl group, an ethyl group, and a propyl group are preferable.
In the formula 1, the position of the hydroxyl group (—OH) group may be between two alkylite methyl groups (—CH ₂ —S—R ¹ (R ² )) or next to the R ³ group.

  The phenol derivative used in the present invention is particularly preferably 2,4-bis (octylthiomethyl) -6-methylphenol. Such phenol derivatives are commercially available, such as Irganox 1520 manufactured by Ciba Specialty Chemicals, Antage HP-400 manufactured by Kawaguchi Chemical Co., Ltd., and the like.

(filler)
The tire rubber composition of the present invention may contain various fillers. The filler is not particularly limited and may be appropriately selected depending on the application. Examples thereof include inorganic fillers. Examples of the inorganic filler include silica, clay, talc, calcium carbonate and the like.

(Combination ratio of tire rubber composition)
The tire rubber composition of the present invention, with respect to the diene rubber 100 parts by weight, the nitrogen adsorption specific surface area _(N 2 SA) of carbon black is less than ^{30 m} 2 / g or more ^{80 m} 2 / g 15 to 70 parts by mass of the 0.5-10 mass parts of phenol derivatives represented by Formula 1 are blended.
If the blending amount of the carbon black is less than 15 parts by mass, the rigidity is insufficient, and conversely if it exceeds 70 parts by mass, exothermic properties, initial and post-aging elongation at break, and ozone resistance deteriorate.
When the compounding amount of the phenol derivative represented by the above formula 1 is less than 0.5 parts by mass, the addition amount is too small to achieve the effects of the present invention. Conversely, when it exceeds 10 mass parts, exothermic property will deteriorate.

A more preferable blending amount of the carbon black is 25 to 50 parts by mass with respect to 100 parts by mass of the diene rubber.
A more preferable blending amount of the phenol derivative is 1 to 8 parts by mass with respect to 100 parts by mass of the diene rubber.

  In addition to the components described above, the rubber composition for tires of the present invention is generally blended with a rubber composition such as a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, various oils, an anti-aging agent, and a plasticizer. Various additives that have been used 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 for a tire of the present invention can be used for producing 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.

Reference Example 1, Examples 1 to 3 and Comparative Examples 1 to 6
Preparation of sample In the composition (parts by mass) shown in Table 1, the components excluding the vulcanization system (vulcanization accelerator, sulfur) were kneaded for 5 minutes with a 1.7 liter closed Banbury mixer, and then released outside the mixer. And cooled to room temperature. Subsequently, the composition was kneaded with a roll by adding a vulcanization system to obtain a rubber composition. Next, the obtained rubber composition was press vulcanized at 160 ° C. for 20 minutes in a predetermined mold to prepare a vulcanized rubber test piece. The physical properties of the obtained vulcanized rubber specimens were measured by the following test methods.

Elongation at break: The elongation at break at room temperature (23 ° C.) was measured according to JIS K6251. With reference example 1 as the reference (100), the larger the index, the better the elongation at break.
Tensile elongation retention after heat aging: Tensile test dumbbell test pieces composed of the above vulcanized rubber test pieces are left in a gear oven at a predetermined temperature and time, and then measured for elongation at break according to JIS K6251. Then, the retention was obtained by comparison with the elongation at break before aging, and the obtained retention was indicated by an index with reference example 1 being 100. The larger the index, the higher the elongation at break after heat aging and the better.
Exothermic property: Tan δ at 60 ° C. was measured at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz in accordance with JIS K6394. It was shown as an index with the value of Reference Example 1 being 100. The smaller the index, the lower the exothermic property.
Bending crack growth property (crack resistance): A bending crack growth test was conducted in accordance with JIS K6260, and the value of Reference Example 1 was shown as an index of 100. The smaller the index, the smaller the crack growth and the better.
The results are shown in Table 1.

* 1: NR (STR20 made in Thailand)
* 2: Carbon black (Nittan Carbon Co., Ltd., Niteron 10N, N ₂ SA = 31 m ² / g)
* 3: Carbon black (manufactured by Shin-Nikka Carbon Co., Ltd., Niteron 300IH, N ₂ SA = 115 m ² / g)
* 4: Anti-aging agent 1 (Seiko Chemical Co., Ltd., non-flex RD)
* 5: Anti-aging agent 2 (Seiko Chemical Co., Ltd., Ozonon 6C)
* 6: Phenol derivative (manufactured by Kawaguchi Chemical Industry Co., Ltd., Antage HP-400)
* 7: Stearic acid (manufactured by NOF Corporation, stearic acid YR)
* 8: Zinc flower (Zodo oxide, manufactured by Shodo Chemical Industry Co., Ltd.)
* 9: Sulfur (manufactured by Tsurumi Chemical Co., Ltd., fine powdered sulfur with Jinhua seal oil)
* 10: Vulcanization accelerator (Ouchi Shinsei Chemical Co., Ltd., Noxeller NS-P)

As is clear from Table 1 above, the tire rubber compositions prepared in Examples 1 to 3 were formulated with a specific amount of carbon black having specific characteristics in a specific diene rubber and a specific phenol. Since a specific amount of the derivative is blended, the exothermic property, the elongation at break after initial aging and crack resistance, and the crack resistance are superior to the conventional representative reference example 1. From these results, it is understood that the tire rubber compositions prepared in Examples 1 to 3 are particularly suitable for use in tire belt cushions and upper bead fillers.
On the other hand, since the comparative example 1 does not mix | blend a phenol derivative, the elongation at break at the initial stage and after aging is getting worse. In particular, since Comparative Example 1 does not contain an anti-aging agent, the crack resistance is remarkably deteriorated.
Comparative Example 2 is an example in which an anti-aging agent was blended without using a phenol derivative, and although low exothermic property was obtained, elongation at break and crack resistance after aging were deteriorated.
In Comparative Example 3, since the nitrogen adsorption specific surface area (N ₂ SA) of carbon black exceeds the upper limit specified in the present invention and no phenol derivative is blended, low exothermic property cannot be obtained, and crack resistance also deteriorates. ing.
In Comparative Example 4, the blending amount of carbon black was less than the lower limit specified in the present invention, and no phenol derivative was blended, so that low exothermic properties were not obtained.
In Comparative Example 5, since the blending amount of the phenol derivative exceeded the upper limit defined in the present invention, low exothermic property was not obtained.
In Comparative Example 6, since the nitrogen adsorption specific surface area (N ₂ SA) of carbon black exceeded the upper limit defined in the present invention, low exothermic property was not obtained.

Reference Example 2, Examples 4-7 and Comparative Examples 7-13
Preparation of sample In the composition (parts by mass) shown in Table 2, the components excluding the vulcanization system (vulcanization accelerator, sulfur) were kneaded for 5 minutes in a 1.7 liter closed Banbury mixer, and then released outside the mixer. And cooled to room temperature. Subsequently, the composition was kneaded with a roll by adding a vulcanization system to obtain a rubber composition. Next, the obtained rubber composition was press vulcanized at 160 ° C. for 20 minutes in a predetermined mold to prepare a vulcanized rubber test piece. The physical properties of the obtained vulcanized rubber specimens were measured by the following test methods.

Elongation at break: The elongation at break at room temperature (23 ° C.) was measured according to JIS K6251. With reference example 2 as the reference (100), the larger the index, the better the elongation at break.
Breaking elongation after heat aging: The tensile test dumbbell test piece made of the above vulcanized rubber test piece was left in a gear oven at 90 ° C. for 48 hours, and then the breaking elongation at room temperature was measured according to JIS K6251. Using Reference Example 2 as a reference (100), the larger the index, the better the elongation at break after aging.
Exothermic property: Tan δ at 60 ° C. was measured at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz in accordance with JIS K6394. It was shown as an index with the value of Reference Example 2 as 100. The smaller the index, the lower the exothermic property.
Ozone resistance: measured in accordance with JIS K6259.
The static ozone test was evaluated in a cracked state after 48 hours at an ozone concentration of 50 ppm, 40 ° C., and a strain of 20 ± 2%.
The dynamic ozone test was evaluated in a cracked state after 96 hours at an ozone concentration of 50 ppm, 40 ° C., and a strain of 20 ± 2%.
The results are shown in Table 2.

* 11: NR (Thailand RSS # 3)
* 12: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.)
* 13: Carbon black (manufactured by Cabot Japan, Showa Black N220, N ₂ SA = 111 m ² / g)
* 14: Carbon black (manufactured by Tokai Carbon Co., Ltd., Seast N, N ₂ SA = 74 m ² / g)
* 15: Carbon black (manufactured by Nippon Kayaku Carbon Co., Ltd., Niteron # 10, N ₂ SA = 49 m ² / g)
* 16: Oil (Showa Shell Sekiyu KK, Extra 4S)
* 17: Anti-aging agent 3 (Sumitomo Chemical Co., Ltd., Antigen 6C)
* 18: Anti-aging agent 4 (Seiko Chemical Co., Ltd., non-flex RD-Y)
* 19: Phenol derivative (manufactured by Kawaguchi Chemical Co., Ltd., Antage HP-400)
* 20: Zinc flower (Zodo oxide, manufactured by Shodo Chemical Industry Co., Ltd.)
* 21: Stearic acid (manufactured by NOF Corporation, bead stearic acid)
* 22: Vulcanization accelerator (manufactured by FLEXSYS, SANTOCURE TBBS)
* 23: Sulfur (manufactured by Tsurumi Chemical Co., Ltd., fine powdered sulfur with Jinhua seal oil)

As is apparent from Table 2 above, the tire rubber compositions prepared in Examples 4 to 7 were formulated with specific amounts of carbon black having specific characteristics in specific diene rubbers, and specific phenols. Since a specific amount of the derivative is blended, the exothermic property, the elongation at break after initial aging and after the aging, and the ozone resistance are excellent as compared with the conventional representative reference example 2. From this result, it can be seen that the tire rubber compositions prepared in Examples 4 to 7 are particularly suitable for use in tire sidewalls.
On the other hand, since the comparative example 7 does not mix | blend a phenol derivative, the elongation at break at the initial stage and after aging is getting worse.
Comparative Examples 8 and 9 are examples in which an antiaging agent was blended without using a phenol derivative, and the static ozone properties were deteriorated.
In Comparative Examples 10 and 11, since the blending amount of carbon black exceeds the upper limit specified in the present invention without using a phenol derivative, the elongation at break at the initial stage and after aging deteriorates, and the ozone resistance is also improved. I couldn't.
Since the compounding quantity of the phenol derivative exceeds the upper limit prescribed | regulated by this invention in the comparative example 12, exothermic property is getting worse.
In Comparative Example 13, since the nitrogen adsorption specific surface area (N ₂ SA) of carbon black exceeded the upper limit defined in the present invention, low exothermic property was not obtained.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall 3 Tread 31 Under tread 4 Carcass layer 5 Bead core 6 Bead filler 62 Upper bead filler 7 Belt layer 8 Belt cushion 9 Inner liner

Claims (6)

To natural rubber and / or diene rubber 100 parts by mass including isoprene rubber, a nitrogen adsorption specific surface area _(N 2 SA) of ^{30 m} 2 / g or more ^{80 m} 2 / g less than the carbon black from 15 to 70 parts by weight and the following formula A rubber composition for tires, comprising 0.5 to 10 parts by mass of the phenol derivative represented by 1.
[Chemical 1]

(In Formula 1, R ¹ and R ² each independently represents an alkyl group having 6 to 12 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms)   2. The tire rubber composition according to claim 1, wherein a proportion of natural rubber and / or isoprene rubber is 50 parts by mass or more in 100 parts by mass of the diene rubber.   2. The tire rubber composition according to claim 1, wherein the diene rubber further includes a butadiene rubber, and a proportion of the butadiene rubber is 50 to 80 parts by mass in 100 parts by mass of the diene rubber. object.   A pneumatic tire using the rubber composition for a tire according to claim 2 as a belt cushion.   A pneumatic tire using the rubber composition for a tire according to claim 2 as an upper bead filler.   A pneumatic tire using the tire rubber composition according to claim 3 as a sidewall.

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