JP2011174008A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition which has both high braking properties and low rolling resistance on wet road surfaces, while maintaining a high elastic modulus, and has improved processability, and to provide a pneumatic tire using the same. <P>SOLUTION: There are provided the rubber composition characterized by comprising 100 pts.mass of a dienic rubber, 30 to 150 pts.mass of silica having a BET specific surface area of 100 to 300 m<SP>2</SP>/g, and 0.1 to 5 pts.mass of 2-(N, N-dibenzylthiocarbamoylthio)benzothiazole; and the pneumatic tire using the rubber composition for the tread (3). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition and a pneumatic tire using the rubber composition, and more specifically, while maintaining a high elastic modulus, it achieves both high braking / driving performance on a wet road surface and low rolling resistance and processability. The present invention also relates to an improved rubber composition and a pneumatic tire using the same.

With the recent increase in safety awareness and environmental awareness, both high braking / driving performance (wet performance) on wet road surfaces and low rolling resistance are required as tire characteristics.
In order to achieve this object, for example, it is known to blend silica in a tire rubber compound. However, this means has a problem that the elastic modulus is lowered. In addition, when silica is used, the thermal conductivity is lower than that of carbon black, so that the vulcanization rate is slowed, and there is a concern that the productivity is deteriorated.

  The following Patent Document 1 discloses a rubber composition characterized by compounding 0.3 to 5.0 parts by weight of a specific mercaptobenzothiazole derivative with respect to 100 parts by weight of natural rubber and synthetic natural rubber. ing. However, Patent Document 1 does not disclose any technical idea of obtaining a rubber composition having a desired elastic modulus, wet performance, and rolling resistance by combining the derivative and silica having specific characteristics.

JP 2007-327020 A

  Accordingly, an object of the present invention is to provide a rubber composition that achieves both high braking / driving performance on a wet road surface and low rolling resistance while maintaining a high elastic modulus, and has improved workability, and a pneumatic tire using the same. There is to do.

As a result of intensive research, the present inventors have found that the above-mentioned problems can be solved by blending a specific amount of silica having specific characteristics into a diene rubber and blending a specific amount of a specific compound. We were able to complete the invention.
That is, the present invention is as follows.
1. 30 to 150 parts by mass of silica having a BET specific surface area of 100 to 300 m ² / g and 2- (N, N-dibenzylthiocarbamoylthio) benzothiazole represented by the following formula 1 with respect to 100 parts by mass of the diene rubber 0.1-5 mass parts is mix | blended, The rubber composition characterized by the above-mentioned.

[Chemical 1]

2. 2. The rubber composition as described in 1 above, wherein a silane coupling agent is blended in an amount of 5 to 10% by mass based on the silica.
3. A pneumatic tire using the rubber composition according to 1 or 2 above.
4). A pneumatic tire using the rubber composition according to 1 or 2 as a tread.

  According to the present invention, a specific amount of silica having specific characteristics is blended with a diene rubber, and a specific amount of a specific compound is blended to maintain a high elastic modulus while maintaining high braking / driving on a wet road surface. Thus, it is possible to provide a rubber composition that achieves both high performance and low rolling resistance and improved workability, and a pneumatic tire using the rubber composition.

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 for a passenger car.
In FIG. 1, the 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 fiber cords are 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. In the tread 3, a belt layer 7 is disposed over the circumference of the tire outside the carcass layer 4. In the bead portion 1, a rim cushion 8 is disposed at a portion in contact with the rim.
The rubber composition of the present invention described below is useful for various members for tires as described above, and particularly useful for the tread 3.

(Diene rubber)
As the diene rubber component used in the present invention, any diene rubber that can be blended in the rubber composition can be used. For example, natural rubber (NR), isoprene rubber (IR), 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.
Among these diene rubbers, SBR and BR are preferable as the diene rubber from the viewpoint of the effect of the present invention.

(silica)
The silica used in the present invention needs to have a BET specific surface area (measured in accordance with ISO5794 Annex E) of 100 to 300 m ² / g.
If the BET specific surface area is less than 100 m ² / g, the elastic modulus decreases, which is not preferable. Conversely, if it exceeds 300 m ² / g, the vulcanization rate of the rubber composition is delayed and the processability is greatly deteriorated due to an increase in viscosity, which is not preferable.
A preferred BET specific surface area is 110 to 240 m ² / g. More preferably, it is 140-210 m < ² > / g.

(Silane coupling agent)
In the present invention, it is preferable to use a silane coupling agent in order to increase the reinforcing effect of the rubber matrix by silica. The silane coupling agent used is not particularly limited, but is preferably a sulfur-containing silane coupling agent, such as 3-octanoylthiopropyltriethoxysilane, 3-propionylthiopropyltrimethoxysilane, bis- (3-bistriethoxy). Silylpropyl) -tetrasulfide, bis- (3-bistriethoxysilylpropyl) -disulfide, 3-mercaptopropyltrimethoxysilane and the like.
5-10 mass% is preferable with respect to the said silica, and, as for the compounding quantity of a silane coupling agent, 7-10 mass% is more preferable.

  In the present invention, it is essential to use 2- (N, N-dibenzylthiocarbamoylthio) benzothiazole (hereinafter referred to as a compound represented by Formula 1) represented by Formula 1 below.

[Chemical 2]

The compound represented by Formula 1 is a known compound, and is disclosed in Patent Document 1, for example. It is also commercially available.
By combining the specific amount of the compound represented by the formula 1 and the specific amount of silica and blending it with the rubber composition, both wet performance and low rolling resistance are achieved while maintaining a high elastic modulus. In addition, a rubber composition having improved processability and a pneumatic tire using the rubber composition can be provided.

(filler)
The rubber composition of the present invention can contain various fillers in addition to the silica. The filler is not particularly limited and may be appropriately selected depending on the application. Examples thereof include carbon black and inorganic filler. Examples of the inorganic filler include clay, talc, and calcium carbonate. Of these, carbon black is preferred.

(Rubber composition ratio)
In the rubber composition of the present invention, 30 to 150 parts by mass of silica having a BET specific surface area of 100 to 300 m ² / g and 100 to 300 parts by mass of the diene rubber and 0.1 to 5 of the compound represented by the above formula 1 are used. It is characterized by blending parts by mass.
When the blending amount of the silica is less than 30 parts by mass, desired wet performance and rolling resistance cannot be compatible. Conversely, if it exceeds 150 parts by mass, the Mooney viscosity increases and processing becomes difficult, which is not preferable.
When the compounding amount of the compound represented by Formula 1 is less than 0.1 parts by mass, the addition amount is too small to achieve the effects of the present invention. Conversely, when it exceeds 5 mass parts, wet performance will deteriorate.

A preferable blending amount of the silica is 40 to 120 parts by mass with respect to 100 parts by mass of the diene rubber. More preferably, it is 40-100 mass parts.
The compounding quantity of the compound represented by the said preferable Formula 1 is 0.2-3 mass parts with respect to 100 mass parts of diene rubbers.

  In addition to the components described above, the rubber composition 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 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.

  Applications of the rubber composition of the present invention include belt conveyors, hoses, tires, and the like, but tire applications are particularly preferable, and they are particularly preferably used for treads.

  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.

Standard example, Examples 1-6 and Comparative Examples 1-5
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 put into the Banbury mixer again, and a vulcanization system was added and kneaded 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 unvulcanized rubber composition and vulcanized rubber test piece were measured by the following test methods.

Vulcanization rate test: In accordance with JIS 6300, the time (T95, minutes) to reach a vulcanization degree of 95% at an amplitude of 1 degree and 160 ° C. was measured with a vibration disk vulcanization tester. The results are shown as an index with the value of the standard example being 100. The smaller the index, the faster the vulcanization speed and the better the productivity.
Elastic modulus @ 0 ° C. Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, the elastic modulus was measured under the conditions of initial strain = 10%, amplitude = ± 2%, frequency = 20 Hz, and temperature 0 ° C. The value of the standard example was set to 100, and displayed as an index. It shows that an elastic modulus is so high that a numerical value is large.
tan δ (0 ° C.): Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, tan δ (0 ° C.) was measured under the conditions of initial strain = 10%, amplitude = ± 2%, frequency = 20 Hz. Wet performance was evaluated. The results are shown as an index with the standard example being 100. It shows that wet performance is so favorable that an index | exponent is large.
tan δ (60 ° C.): 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, With this value, rolling resistance was evaluated. The results are shown as an index with the standard example being 100. A lower index indicates better rolling resistance.
The results are also shown in Table 1.

* 1: SBR (NS460 manufactured by Nippon Zeon Co., Ltd.)
* 2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.)
* 3: Silica-1 (Evonik Degussa Japan Co., Ltd. ULTRASIL VN3GR, BET specific surface area = 175 m ² / g)
* 4: Silane coupling agent (Si69 manufactured by Evonik Degussa Japan Co., Ltd., compound name = bis-triethoxysilylpropyltetrasulfide)
* 5: Carbon black (Show Black N339 manufactured by Cabot Japan Co., Ltd.)
* 6: Zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd., three types of zinc oxide)
* 7: Stearic acid (beef stearic acid YR manufactured by NOF Corporation)
* 8: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu KK)
* 9: Sulfur (Hosoi Chemical Co., Ltd., oil-treated sulfur)
* 10: DBZM (2- (N, N-dibenzylthiocarbamoylthio) benzothiazole)
* 11: Vulcanization accelerator-1 (Sunshin CM-G manufactured by Sanshin Chemical Industry Co., Ltd.)
* 12: Vulcanization accelerator-2 (PERKACIT DPG grs manufactured by FLEXSYS)

As is clear from Table 1 above, the rubber compositions prepared in Examples 1 to 6 contain a specific amount of silica having specific characteristics in the diene rubber and a specific amount of a specific compound. Therefore, compared to the conventional typical standard example, while maintaining a high elastic modulus, both high braking / driving performance on a wet road surface and low rolling resistance are compatible, and processability is also improved.
On the other hand, Comparative Example 1 is an example in which the amount of the vulcanization accelerator is increased without compounding the compound represented by Formula 1, and the wet performance is deteriorated.
Comparative Example 2 is an example in which the blending amount of silica is less than the lower limit specified in the present invention, and the blending amount of carbon black is increased, and wet performance and rolling resistance are deteriorated.
In Comparative Example 3, since the compound represented by Formula 1 exceeds the upper limit defined in the present invention, the wet performance is deteriorated.

1 Bead part 2 Side wall 3 Tread 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims (4)

30 to 150 parts by mass of silica having a BET specific surface area of 100 to 300 m ² / g and 2- (N, N-dibenzylthiocarbamoylthio) benzothiazole represented by the following formula 1 with respect to 100 parts by mass of the diene rubber 0.1-5 mass parts is mix | blended, The rubber composition characterized by the above-mentioned.
[Chemical 1]

  The rubber composition according to claim 1, wherein a silane coupling agent is blended in an amount of 5 to 10% by mass with respect to the silica.   A pneumatic tire using the rubber composition according to claim 1.   A pneumatic tire using the rubber composition according to claim 1 for a tread.

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