JP2010174232A - Rubber composition for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire, which can produce the tire being excellent in traveling property on a wet road surface. <P>SOLUTION: The rubber composition for the tire contains 100 pts.mass of a rubber component comprising 100 mass% of a diene-based rubber and 0.5-30 pts.mass of a polystyrene-hydrofined vinylpolyisoprene-polystyrene triblock copolymer based on 100 pts.mass of the rubber composition. Preferably, the rubber composition further contains 10-80 pts.mass of silica. Further, the polystyrene-hydrogenated vinylpolyisoprene-polystyrene triblock copolymer may be the copolymer in which a styrene content is 5-30 mass%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition for tires. In particular, the present invention relates to a tire rubber composition capable of producing a tire excellent in running performance on a wet road surface.

  An example in which a styrene block copolymer is blended with a tire rubber composition is known. For example, Patent Document 1 can form a tire excellent in braking performance and fuel consumption performance, and further, as a rubber composition excellent in mechanical strength and fatigue resistance, a specific non-conjugated polyene copolymer, A rubber composition containing a diene rubber, a copolymer containing an aromatic vinyl polymer block and a conjugated diene polymer block, or a hydrogenated product thereof is disclosed.

  Patent Document 2 and Patent Document 3 describe a tire containing a diene rubber, a reinforcing agent, and a polystyrene-vinylisoprene triblock copolymer as a rubber composition that improves wear resistance and realizes low rolling resistance. A rubber composition is disclosed.

  Patent Document 4 discloses that a polystyrene-poly (ethylene-ethylene / butylene) block-polystyrene copolymer is used as an adhesive layer for bonding an inner liner layer to a rubber composition member.

  Patent Document 5 discloses a heavy rubber composition comprising a solid rubber, a diene-based liquid rubber, and styrene as a rubber composition that has a sufficient molding processability and gives a vulcanizate having a high hardness when the resulting molded body is vulcanized. It discloses the use of a rubber composition containing a copolymer block and a copolymer containing a polymer block composed of a diene monomer such as isoprene or butadiene.

  Patent Document 6 shows a polystyrene- (hydrogenated vinylisoprene) -polystyrene block copolymer and a terpene as a high-damping elastomer composition exhibiting high damping properties, hardness in an appropriate range, and low hardness temperature dependence. A rubber composition containing a phenol resin and a butadiene block liquid polymer is disclosed.

International Publication No. 2005/105913 Pamphlet JP 2004-010881 A Japanese Patent Laid-Open No. 2004-002622 JP 2007-276235 A Japanese Patent Laid-Open No. 06-220256 JP 2005-105209 A

  Tires are required to improve running performance on wet road surfaces. This invention provides the rubber composition for tires which can produce the tire excellent in the running property on a wet road surface.

  The present invention is a tire comprising 100 parts by mass of a diene rubber 100 parts by mass and 0.5-30 parts by mass of a polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer with respect to 100 parts by mass of the rubber component. Rubber composition for use.

  The rubber composition of the present invention preferably further contains 10 to 80 parts by mass of silica with respect to 100 parts by mass of the rubber component.

  In the rubber composition of the present invention, preferably, the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer has a styrene content of 5 to 30% by mass.

  The present invention improves the low temperature tan δ (tan δ at 0 ° C.) of a rubber composition by blending a polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer with a rubber component comprising 100% by mass of a diene rubber. In addition, the high temperature tan δ (tan δ at 60 ° C.) and specific gravity of the rubber composition can be reduced. By improving the low temperature tan δ, the wet running performance of a tire made from the rubber composition can be improved. In addition, due to the decrease in high temperature tan δ, the heat build-up of a tire made from the rubber composition is lowered, and as a result, the rolling resistance is lowered, and the fuel efficiency of an automobile equipped with the tire made from the rubber composition is improved. Can do. Further, the reduction in specific gravity can improve the fuel efficiency of an automobile equipped with a tire made from the rubber composition.

  The rubber composition for tires of the present invention comprises 100 parts by mass of a rubber component composed of 100% by mass of a diene rubber and 100 parts by mass of the rubber component with a polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer 0.5 to 30 parts by mass are included.

The rubber component used in the present invention is composed of 100% by mass of a diene rubber. That is, the rubber component used in the present invention does not include rubber components other than the diene rubber. As the diene rubber, a known diene rubber having a double bond in the main chain can be used without limitation, but a polymer or copolymer rubber having a conjugated diene compound as a main monomer is preferable. The diene rubber includes natural rubber (NR) and hydrogenated rubber.
Such diene rubbers include natural rubber (NR), isoprene rubber (IR), styrene / butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile / butadiene rubber (NBR), and nitrile. Examples thereof include rubber and hydrogenated nitrile rubber. Among these, natural rubber (NR), isoprene rubber (IR), styrene / butadiene rubber (SBR), and butadiene rubber (BR) are preferable, and butadiene rubber (BR) is particularly preferable. Diene rubber can be used alone or in combination of two or more.
As natural rubber (NR), natural rubber standardized by Green Book (international quality packaging standard for various grades of natural rubber) can be used. As the isoprene rubber (IR), those having a specific gravity of 0.91 to 0.94, Mooney viscosity [ML _{1 + 4} (100 ° C.), JIS K6300] of 30 to 120 are preferably used. As the styrene-butadiene rubber (SBR), those having a specific gravity of 0.91 to 0.98, Mooney viscosity [ML _{1 + 4} (100 ° C.), JIS K6300] of 20 to 120 are preferably used. As the butadiene rubber (BR), those having a specific gravity of 0.90 to 0.95, Mooney viscosity [ML _{1 + 4} (100 ° C.), JIS K6300] of 20 to 120 are preferably used.

  The polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer used in the present invention is a polystyrene block represented by the following formula (1) and a hydrogenated vinyl polyisoprene represented by the following formula (2). A triblock copolymer in which a block (that is, a poly (1-isopropylethylene) block) is bonded.

The polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer is obtained by hydrogenating a vinyl polyisoprene block of a polystyrene-vinyl polyisoprene-polystyrene triblock copolymer. If the vinyl polyisoprene block is not hydrogenated, that is, if a double bond remains in the side chain of the vinyl polyisoprene block, crosslinking is not preferable.
The molecular weight of the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer is preferably 30,000 to 300,000, more preferably 80,000 to 250,000. When the molecular weight is less than 30,000, mechanical properties such as strength and elongation at break of the block copolymer itself may be deteriorated. Further, when the molecular weight exceeds 300,000, it becomes difficult to mix with rubber.
The polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer preferably has a styrene content of 5 to 30% by mass, more preferably 10 to 20% by mass. If the styrene content is too small, the hardness is excessively decreased. Conversely, if the styrene content is excessive, the hardness is excessively increased.
Such polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymers are obtained from Kuraray Co., Ltd. under the trade names of Hibler 7125 (styrene content 20% by mass) and Hibler 7311 (styrene content 12% by mass). can do.

  In the rubber composition of the present invention, the blending amount of the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer is 0.5 to 30 parts by mass, preferably 2 to 25 parts per 100 parts by mass of the rubber component. It is a mass part, More preferably, it is 5-20 mass parts. If the blending amount of the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer is too small, sufficient improvement in the low temperature tan δ cannot be achieved, and conversely if too large, the breaking strength decreases.

The rubber composition of the present invention preferably further contains silica.
The silica used for this invention is not specifically limited, The arbitrary silica conventionally mix | blended with the rubber composition for tires and others can be used.
In the rubber composition of the present invention, the compounding amount of silica is preferably 10 to 80 parts by mass and more preferably 20 to 60 parts by mass with respect to 100 parts by mass of the rubber component. By blending silica, the low temperature tan δ can be further improved, and the high temperature tan δ can be lowered. When there are too many compounding quantities of a silica, the mixing workability fall and exothermic property will increase.

  In addition to the components described above, the rubber composition of the present invention includes a reinforcing agent / filler such as carbon black, a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, a plasticizer, various oils, an antiaging agent, and the like. Various additives generally blended for rubber compositions can be blended, and such additives can be kneaded by a general method into a composition and used for vulcanization or crosslinking. . As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

The rubber composition for tires of the present invention is suitably used for treads of pneumatic tires, and particularly suitably used for studless tires and tires for low fuel consumption passenger cars.
As a method for producing a pneumatic tire using the rubber composition of the present invention, a conventional method can be used. For example, an inner liner is attached to a cylinder on a tire molding drum, and members used in normal tire manufacturing such as a carcass layer and a belt layer made of unvulcanized rubber are sequentially laminated thereon, and finally the present invention is applied. A desired pneumatic tire can be manufactured by laminating a tread layer prepared from a rubber composition, removing a drum to obtain a green tire, and then heat vulcanizing the green tire according to a conventional method.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example.

The raw materials used in the examples are as follows.
Natural rubber: RSS # 3
Butadiene rubber: Nipol BR 1220 manufactured by Nippon Zeon Co., Ltd.
Non-conjugated polyene: Mitsui Chemicals, Ltd. MITSUI EPT4070
Polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer: Kuraray Hybra 7125 (styrene content 20% by mass) (hereinafter also referred to as “hydrogenated SVIS-1”) and Kuraray Hybra 7311 ( Styrene content 12 mass%) (hereinafter also referred to as “hydrogenated SVIS-2”)
Carbon black: Seast KHP manufactured by Tokai Carbon Co., Ltd.
Silica: ULTRASIL VN-3G manufactured by UNITED SILICA INDUSTRIAL
Zinc Hana: Zinc Oxide 3 types manufactured by Shodo Chemical Co., Ltd. Stearic acid: Beads stearic acid manufactured by NOF Corporation Anti-aging agent: Santflex 6PPD (hereinafter also referred to as “anti-aging agent 1”) manufactured by Flexis Co., Ltd. and Ouchi Shinokku Kogyo Co., Ltd. no crack 224 (hereinafter also referred to as "anti-aging agent 2")
Wax: Sunnock, Ouchi Shinsei Chemical Co., Ltd. Silane coupling agent: Si69, manufactured by Evonik Degussa Japan
Oil: Extract No. 4 S manufactured by Showa Shell Sekiyu KK
Sulfur: Hosoi Chemical Industry Co., Ltd. Oil Processing Sulfur Vulcanization Accelerator: Ouchi Shinsei Chemical Co., Ltd. Noxeller CZ (hereinafter also referred to as “vulcanization accelerator 1”) and Sumitomo Chemical Co., Ltd. Also referred to as “sulfur accelerator 2”.)

  The evaluation items used in the following examples were measured by the following method.

[specific gravity]
A rubber composition is molded into a sheet, and vulcanized under conditions of 170 ° C. for 15 minutes to produce a vulcanized rubber sheet. The vulcanized rubber sheet thus produced has a specific gravity test method described in JIS K6220-1. It was measured by our substitution method. The lower the specific gravity of the rubber composition, the better the fuel efficiency of an automobile equipped with a tire made using the rubber composition.

[Tensile test]
A rubber composition is molded into a sheet, and vulcanized at 170 ° C. for 15 minutes to produce a vulcanized rubber sheet. The produced vulcanized rubber sheet is punched out and described in JIS K6251 (2001) A No. 3 dumbbell specimen was prepared. Using this test piece, in accordance with the method specified in JIS K6251, measurement temperature 25 ° C., subjected to tensile test at a tensile rate of 500 mm / min conditions, the 100% modulus (tensile stress when elongation 100%) M ₁₀₀ (MPa ), 300% modulus (tensile stress at 300% elongation) M ₃₀₀ (MPa), tensile strength T _B (MPa) and elongation at break E _B (%) were measured. The larger the 100% modulus, 300% modulus, tensile strength, and elongation at break, the more preferable.

[Tan δ]
A rubber composition is molded into a sheet, and vulcanized at 170 ° C. for 15 minutes to produce a 2 mm thick vulcanized rubber sheet. A viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Was used to measure loss tangent tan δ (an index of vibration damping) under the conditions of measurement temperatures of 0 ° C. and 60 ° C., frequency of 20 Hz, initial strain of 10%, and amplitude of ± 2%. Tan δ at 0 ° C. is expressed as tan δ (0 ° C.), and tan δ at 60 ° C. is expressed as tan δ (60 ° C.). The larger the tan δ (0 ° C.), the better the wet running performance of the tire. Further, the lower the tan δ (60 ° C.), the lower the exothermic property of the tire, thereby lowering the rolling resistance of the tire, and as a result, the fuel efficiency of the automobile equipped with the tire is improved.

Example 1
The above raw materials were blended at a blending ratio shown in Table 1 to prepare a rubber composition. The prepared rubber composition was evaluated for specific gravity, 100% modulus, 300% modulus, tensile strength, elongation at break, tan δ (0 ° C.) and tan δ (60 ° C.). The evaluation results are shown in Table 1.

Comparative Example 1
A rubber composition was prepared and evaluated in the same manner as in Example 1 except that the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer was not blended in Example 1. The evaluation results are shown in Table 1.

Comparative Example 2
In Example 1, the rubber composition was changed to natural rubber / butadiene rubber = 50 parts by mass / 30 parts by mass, and 20 parts by mass of non-conjugated polyene (MITSUI EPT4070 manufactured by Mitsui Chemicals, Inc.) was additionally blended. A rubber composition was prepared and evaluated. The evaluation results are shown in Table 1.

  From the comparison between Example 1 and Comparative Example 1, it can be seen that when the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer is blended, the specific gravity decreases and tan δ (0 ° C.) increases. From the comparison between Example 1 and Comparative Example 2, when a rubber component other than the diene rubber is blended, tan δ (0 ° C.) decreases, tan δ (60 ° C.) increases, and elongation at break decreases. I understand. That is, it can be seen that the rubber component needs to consist of 100% by weight of a diene rubber.

Example 2
The above raw materials were blended at a blending ratio shown in Table 2 to prepare a rubber composition. In Example 2, the amount of carbon black is reduced to 40 parts by mass in Example 1, and 20 parts by mass of silica is added. The prepared rubber composition was evaluated for specific gravity, 100% modulus, 300% modulus, tensile strength, elongation at break, tan δ (0 ° C.) and tan δ (60 ° C.). The evaluation results are shown in Table 2.

Example 3
In Example 2, polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer (Kuraray Co., Ltd. Hibler 7125, styrene content 20 mass%) was used instead of polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer. A rubber composition was prepared and evaluated in the same manner as in Example 2 except that a polymer (Kuraray Co., Ltd. Hibler 7311, styrene content 12% by mass) was used. The evaluation results are shown in Table 2.

Comparative Example 3
In Example 2, a rubber composition was prepared and evaluated in the same manner as in Example 2 except that the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer was not blended. The evaluation results are shown in Table 2.

  From the comparison between Example 2 and Example 3 and Comparative Example 3, it can be seen that when a polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer is blended, the specific gravity decreases and tan δ (0 ° C.) increases. . Further, from comparison between Example 1 and Example 2, it can be seen that tan δ (0 ° C.) is further increased when silica is added.

Example 4
The above raw materials were blended at a blending ratio shown in Table 3 to prepare a rubber composition. In Example 4, the amount of silica in Example 2 was increased to 60 parts by mass, the amount of carbon black was reduced to 20 parts by mass, and the amount of the silane coupling agent was increased to 5 parts by mass. The prepared rubber composition was evaluated for specific gravity, 100% modulus, 300% modulus, tensile strength, elongation at break, tan δ (0 ° C.) and tan δ (60 ° C.). The evaluation results are shown in Table 3.

Example 5
In Example 4, instead of polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer (Hibler 7125 manufactured by Kuraray Co., Ltd., styrene content 20 mass%), polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer was used. A rubber composition was prepared and evaluated in the same manner as in Example 4 except that a polymer (Kuraray Co., Ltd. Hibler 7311, styrene content 12% by mass) was used. The evaluation results are shown in Table 3.

Example 6
Example 4 except that the blending amount of polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer (Kuraray Hibler 7125, styrene content 20% by mass) was changed to 20 parts by mass in Example 4. A rubber composition was prepared and evaluated in the same manner as described above. The evaluation results are shown in Table 3.

Example 7
In Example 6, instead of a polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer (Hiblar 7125 manufactured by Kuraray Co., Ltd., styrene content 20% by mass), a polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer was used. A rubber composition was prepared and evaluated in the same manner as in Example 6, except that a polymer (Kuraray Co., Ltd. Hibler 7311, styrene content 12% by mass) was used. The evaluation results are shown in Table 3.

Comparative Example 4
In Example 4, a rubber composition was prepared and evaluated in the same manner as in Example 4 except that the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer was not blended. The evaluation results are shown in Table 3.

  From a comparison between Examples 4 to 7 and Comparative Example 4, it can be seen that when a polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer is blended, tan δ (0 ° C.) increases and the specific gravity decreases. Further, from the comparison between Example 4 and Example 6 and the comparison between Example 5 and Example 7, as the blending amount of the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer increases, tan δ (0 ° C.) increases. You can see it grows. Further, from the comparison between Example 2 and Example 4 and the comparison between Example 3 and Example 5, it can be seen that tan δ (0 ° C.) is further increased as the amount of silica is increased.

  The rubber composition for tires of the present invention is suitably used for treads of pneumatic tires, and particularly suitably used for studless tires and tires for low fuel consumption passenger cars.

Claims (3)

  A rubber composition for tires comprising 100 parts by mass of a rubber component composed of 100% by mass of a diene rubber and 0.5-30 parts by mass of a polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer with respect to 100 parts by mass of the rubber component. .   The rubber composition according to claim 1, further comprising 10 to 80 parts by mass of silica with respect to 100 parts by mass of the rubber component.   The rubber composition according to claim 1 or 2, wherein the polystyrene-hydrogenated vinyl polyisoprene-polystyrene triblock copolymer has a styrene content of 5 to 30% by mass.