JP2010174231A - 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 an ice road surface and wearing-resistance. <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-poly(ethylene-ethylene/propylene)block-polystyrene copolymer based on 100 pts.mass of the rubber component. Preferably, the rubber composition further contains 10-80 pts.mass of silica. In the rubber composition for the tire, 20°C hardness after vulcanization is preferably 40 to less than 80. <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 friction on ice and wear resistance.

  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 / propylene) block-polystyrene copolymer is used for 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 high-damping property, a hardness within a suitable range, and a high-damping elastomer composition having a small temperature dependency of hardness, as a styrene-based block copolymer, a terpene phenol resin, and a butadiene-based block liquid. A rubber composition containing a polymer is disclosed.

  Patent Document 7 discloses the use of a styrene / ethylene / propylene / styrene copolymer as a component of an adhesive composition.

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 Japanese Patent Laid-Open No. 11-240108

  Tires are required to have improved running performance and wear resistance on icy road surfaces. The present invention provides a rubber composition for a tire that can produce a tire excellent in running performance and wear resistance on an ice road surface.

  In the present invention, 0.5 to 30 parts by mass of a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer is added to 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. It is a rubber composition for tires containing.

  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.

  The rubber composition of the present invention preferably has a 20 ° C. hardness after vulcanization of 40 or more and less than 80.

  The present invention increases the friction coefficient on ice of a rubber composition by blending a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer with a rubber component consisting of 100% by mass of a diene rubber. As a result, it is possible to improve the running performance of the tire made from the rubber composition on the road surface on ice, and to improve the wear resistance of the rubber composition and thus the tire made from the rubber composition. It can be made.

  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 a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer based on 100 parts by mass of the rubber component. 5-30 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), 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-poly (ethylene-ethylene / propylene) block-polystyrene copolymer used in the present invention is a polystyrene block represented by the following formula (1) and a random copolymer represented by the following formula (2). A block copolymer in which a poly (ethylene-ethylene / propylene) block is bonded.

The polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer preferably has a styrene content of 10 to 50% by mass, more preferably 20 to 40% 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.
The molecular weight of the polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer is preferably 100,000 to 500,000, more preferably 200,000 to 400,000. When the molecular weight is less than 100,000, mechanical properties such as strength and elongation at break of the block copolymer itself may be deteriorated. Further, when the molecular weight exceeds 500,000, it becomes difficult to mix with rubber.
Examples of such commercially available polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymers (SEEPS) include “Septon” series 4000 series manufactured by Kuraray Co., Ltd. 4033, septon 4044, septon 4055, septon 4077, and septon 4099.

  In the rubber composition of the present invention, the blending amount of the polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer is 0.5 to 30 parts by mass, preferably 2 to 100 parts by mass of the rubber component. It is -25 mass parts, More preferably, it is 5-20 mass parts. If the blending amount of polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer is too small, sufficient improvement of friction coefficient on ice and wear resistance cannot be achieved. 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 friction coefficient on ice and the wear resistance can be further improved, and the strength can be improved. When there are too many compounding quantities of a silica, the mixing workability fall and exothermic property will increase.

  The rubber composition of the present invention has a 20 ° C. hardness after vulcanization of preferably 40 or more and less than 80, and more preferably 50 or more and less than 70. If the 20 ° C. hardness after vulcanization is too small, the steering stability is lowered. On the other hand, if it is too large, the ride comfort is deteriorated, and the steering stability and braking performance when the road surface is wet are lowered. A rubber composition having a 20 ° C. hardness of 40 or more and less than 80 after vulcanization can be produced by changing the filler, oil, liquid rubber, other compounding agents and the degree of crosslinking.

  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 tire rubber composition of the present invention is suitably used for a tread of a pneumatic tire, and is suitably used for a studless tire, particularly a snow tire.
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-poly (ethylene-ethylene / propylene) block-polystyrene copolymer: Kuraray Septon 4033 (styrene content 30 mass%) (hereinafter also referred to as “SEEPS-1”) and Kuraray Septon 4077 ( Styrene content: 30% by mass) (hereinafter also referred to as “SEEPS-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.

[hardness]
A rubber composition is molded into a sheet, and vulcanized at 170 ° C. for 15 minutes to prepare a vulcanized rubber sheet. The prepared vulcanized rubber sheet is measured at 0 ° C. according to the test method described in JIS K6253. Measurements were made at 20 ° C and 60 ° C.

[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 defined in JIS K6251, a tensile test was performed under the conditions of a measurement temperature of 25 ° C. and a tensile speed of 500 mm / min, and 100% modulus (tensile stress at 100% elongation) M ₁₀₀ (MPa ), 300% modulus (tensile stress at 300% elongation) M ₃₀₀ (MPa), tensile strength T _B (MPa) and elongation at break E _B (%). The larger the 100% modulus, 300% modulus, tensile strength and elongation at break, the more preferable.

[Abrasion resistance]
The rubber composition was vulcanized at 170 ° C. for 15 minutes in a Lambbone wear mold (disk shape with a diameter of 63.5 mm and a thickness of 5 mm) to prepare a vulcanized rubber test piece. Using Iwamoto Seisakusho), the measurement was performed under the condition of a load of 5 kg and a slip rate of 25%, and the amount of wear of the sample was measured. For each table, the wear resistance is indexed according to the following equation, with the amount of wear in the comparative example of each table (however, Table 1 is Comparative Example 1) being 100.
Abrasion resistance = (Abrasion amount of comparative example / Abrasion amount of sample) × 100
It shows that it is excellent in abrasion resistance, so that a numerical value is large.

[Coefficient of friction on ice]
A rubber composition is formed into a sheet, and vulcanized at 170 ° C. for 15 minutes to produce a vulcanized rubber sheet. The prepared vulcanized rubber sheet is attached to a flat cylindrical base rubber, and an inside drum type friction on ice. The friction coefficient on ice was measured with a test machine under the conditions of measurement temperature: −1.5 ° C., load: 0.54 MPa, drum rotation speed: 10 km / h and 15 km / h. The on-ice friction coefficient index is indexed by the following equation for each table, with the on-ice friction coefficient of the comparative example in each table (however, Table 1 is Comparative Example 1) being 100.
Friction coefficient index on ice = (Friction coefficient on ice of sample / Friction coefficient on ice of comparative example) × 100
The larger the value, the better the friction between rubber and ice.

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 hardness, 100% modulus, 300% modulus, tensile strength, elongation at break, wear resistance, and friction coefficient on ice. The evaluation results are shown in Table 1.

Example 2
In Example 1, instead of polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer (Kuraray Co., Ltd. Septon 4033, styrene content 30% by mass), polystyrene-poly (ethylene-ethylene / propylene) A rubber composition was prepared and evaluated in the same manner as in Example 1 except that a block-polystyrene copolymer (Kuraray Septon 4077, styrene content 30% by mass) was used. The evaluation results are shown in Table 1.

Comparative Example 1
In Example 1, a rubber composition was prepared and evaluated in the same manner as in Example 1 except that a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer was not blended. The evaluation results are shown in Table 1.

Comparative Example 2
In Example 1, except that 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 added. A rubber composition was prepared and evaluated in the same manner as described above. The evaluation results are shown in Table 1.

  From comparison between Example 1 and Example 2 and Comparative Example 1, it can be seen that when a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer is blended, the friction coefficient on ice and the wear resistance are increased. Further, from comparison between Example 1 and Comparative Example 2, it can be seen that the compound containing non-conjugated polyene as the rubber component has poor wear resistance and friction coefficient on ice. That is, it can be seen that the rubber component needs to consist of 100% by weight of a diene rubber.

Example 3
The above raw materials were blended at a blending ratio shown in Table 2 to prepare a rubber composition. In Example 3, the compounding amount of carbon black in Example 1 is reduced to 40 parts by mass, and 20 parts by mass of silica and 2 parts by mass of a silane coupling agent are added. The prepared rubber composition was evaluated for hardness, 100% modulus, 300% modulus, tensile strength, elongation at break, wear resistance, and friction coefficient on ice. The evaluation results are shown in Table 2.

Example 4
In Example 3, instead of a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer (Septon 4033 manufactured by Kuraray Co., Ltd.), a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer ( A rubber composition was prepared and evaluated in the same manner as in Example 3 except that Kuraray Septon 4077) was used. The evaluation results are shown in Table 2.

Comparative Example 3
In Example 3, a rubber composition was prepared and evaluated in the same manner as in Example 3 except that the polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer was not blended. The evaluation results are shown in Table 2.

  From the comparison between Example 3 and Example 4 and Comparative Example 3, it can be seen that when a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer is blended, the friction coefficient on ice and the wear resistance are increased.

Example 5
The above raw materials were blended at a blending ratio shown in Table 3 to prepare a rubber composition. In Example 3, the compounding amount of silica was increased to 60 parts by mass, the compounding amount of carbon black was reduced to 10 parts by mass, and the compounding amount of the silane coupling agent was increased to 5 parts by mass. . The prepared rubber composition was evaluated for hardness, 100% modulus, 300% modulus, tensile strength, elongation at break, wear resistance, and friction coefficient on ice. The evaluation results are shown in Table 3.

Example 6
In Example 5, instead of polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer (Septon 4033 manufactured by Kuraray Co., Ltd.), polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer ( A rubber composition was prepared and evaluated in the same manner as in Example 5 except that Kuraray Septon 4077) was used. The evaluation results are shown in Table 3.

Comparative Example 4
In Example 5, a rubber composition was prepared and evaluated in the same manner as in Example 5 except that the polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer was not blended. The evaluation results are shown in Table 3.

  From the comparison between Example 5 and Example 6 and Comparative Example 4, it can be seen that when a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer is blended, the friction coefficient on ice and the wear resistance are increased.

Example 7
The above raw materials were blended at a blending ratio shown in Table 4 to prepare a rubber composition. In Example 7, the amount of oil in Example 3 was increased to 50 parts by mass. The prepared rubber composition was evaluated for hardness, 100% modulus, 300% modulus, tensile strength, elongation at break, wear resistance, and friction coefficient on ice. The evaluation results are shown in Table 4.

Example 8
In Example 7, instead of a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer (Septon 4033 manufactured by Kuraray Co., Ltd.), a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer ( A rubber composition was prepared and evaluated in the same manner as in Example 7 except that Kuraray Septon 4077) was used. The evaluation results are shown in Table 4.

Comparative Example 5
In Example 7, a rubber composition was prepared and evaluated in the same manner as in Example 7 except that the polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer was not blended. The evaluation results are shown in Table 4.

  From the comparison between Example 7 and Example 8 and Comparative Example 5, it can be seen that when a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer is blended, the friction coefficient on ice and the wear resistance are increased.

Example 9
The above raw materials were blended at a blending ratio shown in Table 5 to prepare a rubber composition. Example 9 increases the polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer (Kuraray Co., Ltd. Septon 4033) to 20 parts by mass and the silica content to 40 parts by mass in Example 3. The amount of silane coupling agent is increased to 3 parts by mass, and the amount of oil is reduced to 30 parts by mass. The prepared rubber composition was evaluated for hardness, 100% modulus, 300% modulus, tensile strength, elongation at break, wear resistance, and friction coefficient on ice. The evaluation results are shown in Table 5.

Example 10
In Example 9, instead of a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer (Septon 4033 manufactured by Kuraray Co., Ltd.), a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer ( A rubber composition was prepared and evaluated in the same manner as in Example 9 except that Kuraray Septon 4077) was used. The evaluation results are shown in Table 5.

Comparative Example 6
In Example 9, a rubber composition was prepared and evaluated in the same manner as in Example 9 except that the polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer was not blended. The evaluation results are shown in Table 5.

  From the comparison between Example 9 and Example 10 and Comparative Example 6, when 20 parts by mass of polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer is blended, the friction coefficient on ice and the wear resistance increase. I understand.

  The tire rubber composition of the present invention is suitably used for a tread of a pneumatic tire, and is suitably used for a studless tire, particularly a snow tire.

Claims (3)

  Rubber for tires comprising 100 parts by mass of a rubber component comprising 100% by mass of a diene rubber and 0.5-30 parts by mass of a polystyrene-poly (ethylene-ethylene / propylene) block-polystyrene copolymer with respect to 100 parts by mass of the rubber component. Composition.   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 vulcanized 20 ° C hardness is 40 or more and less than 80.