Rubber composition for tire and tire

Abstract

To solve the problem that performances required for a tire are generally various, among the performances, the tire is required to simultaneously satisfy wet grip performance and abrasion resistance, and the requirements exist in a racing tire for circuit traveling.SOLUTION: A rubber composition for a tire is obtained by blending 5 to 120 pts.mass of a rosin ester resin which has an acid value of 30 mgKOH / g or less and is hydrogenated with respect to 100 pts.mass of diene-based rubber composed of only styrene-butadiene copolymer rubber.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for tires and a tire using the same, and more particularly to a rubber composition for tires capable of maintaining or improving abrasion resistance and improving wet grip performance, and a tire using the same.

Background Art

[0002] Generally, for pneumatic tires for competition, tires for dry road surface driving and tires for wet road surface driving are prepared, and the most suitable tire is selected according to the weather and road surface conditions during driving. Here, as a competition tire for wet road surface driving, in order to enhance wet grip performance, techniques such as blending a large amount of a filler or resin having a high specific surface area are employed, but in the prior art, there is a problem that abrasion resistance decreases.

[0003] In addition, as a technique of blending a rosin-based resin into a rubber composition for tires, it can be found in Patent Documents 1 to 3 below, etc., but for a diene rubber consisting only of a styrene-butadiene copolymer rubber described below, a rosin ester resin having an acid value of 30 mgKOH / g or less and hydrogenated is blended in a specific amount, and the technical idea of maintaining or improving abrasion resistance and improving wet grip performance is not disclosed or suggested at all.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Accordingly, an object of the present invention is to provide a rubber composition for tires that can maintain or improve wear resistance and improve wet grip performance, and a tire using the same. **Means for Solving the Problems**

[0006] As a result of intensive studies by the present inventors, it has been found that by blending a hydrogenated rosin ester resin having an acid value within a specific range and in a specific amount with a diene rubber composed only of a styrene-butadiene copolymer rubber, the above problems can be solved, and the present invention has been completed.

[0007] That is, the present invention provides a rubber composition for tires, characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less is blended with 100 parts by mass of a diene rubber composed only of a styrene-butadiene copolymer rubber. **Effects of the Invention**

[0008] The rubber composition for tires of the present invention is characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less is blended with 100 parts by mass of a diene rubber composed only of a styrene-butadiene copolymer rubber. Therefore, it is possible to provide a rubber composition for tires that can maintain or improve wear resistance and improve wet grip performance, and a tire using the same.

[0009] The rosin ester resin used in the present invention has an acid value of 30 mgKOH / g or less. Therefore, its compatibility with styrene-butadiene copolymer rubber is enhanced compared to resins having a higher acid value, and when a vulcanization accelerator is used, it does not show excessive reactivity, so a decrease in breaking strength and hardness can be suppressed. In addition, since the rosin ester resin is hydrogenated, it exhibits the effect of enhancing compatibility with styrene-butadiene copolymer rubber. It is presumed that this can provide a rubber composition for tires that can maintain or improve wear resistance and improve wet grip performance.

Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in more detail.

[0011] (Diene rubber) The diene rubber used in the present invention consists only of styrene-butadiene copolymer rubber (SBR). The molecular weight and microstructure of SBR are not particularly limited, and it may be end-modified with amines, amides, silyls, alkoxysilyls, carboxyls, hydroxyl groups, etc., or may be epoxidized. The weight average molecular weight (Mw) of SBR is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000. In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are standard polystyrene conversion values obtained by gel permeation chromatography (GPC) measurement.

[0012] (Rosin ester resin) The rosin ester resin used in the present invention can be obtained by reacting a raw material rosin ester such as gum rosin, tall oil rosin, or wood rosin with alcohols and polymerizing in the presence of a catalyst. The esterification reaction and polymerization reaction may be based on known conditions. The obtained rosin ester resin may be purified as necessary, and the color tone of this purified rosin ester resin is usually 10 or less in Gardner color number. The rosin ester resin used in the present invention has an acid value of 30 mgKOH / g or less. When the acid value is 30 mgKOH / g or less, the compatibility with SBR is enhanced, the wet grip performance is improved, and when a vulcanization accelerator is used, it does not show excessive reactivity, and a decrease in breaking strength and hardness can be suppressed. In the present invention, the acid value is more preferably 20 mgKOH / g or less. In addition, the rosin ester resin used in the present invention is hydrogenated. By hydrogenation, the compatibility with styrene-butadiene copolymer rubber is enhanced, and the effect of improving the breaking strength is exhibited. The hydrogenation is preferably carried out until the Hazen unit color number (JIS K0071-1) of the rosin ester resin becomes 200 or less. Also, from the viewpoint of improving the effects of the present invention, the hydroxyl value of the rosin ester resin used in the present invention is preferably 50 mgKOH / g or less, more preferably 30 mgKOH / g or less. When the hydroxyl value is 50 mgKOH / g or less, the compatibility with SBR is enhanced, and the wet grip performance can be further improved. Also, from the viewpoint of improving the effects of the present invention, the weight average molecular weight of the rosin ester resin used in the present invention is preferably 200 to 1800, more preferably 300 to 1500, the glass transition temperature is preferably 20 to 100 °C, more preferably 30 to 90, and the softening point (JIS K6220-1) is preferably 60 to 150 °C, more preferably 70 to 140. As the rosin ester resin in the present invention, commercially available products can be used. For example, KE-359 (hydrogenated rosin ester resin, acid value = 13 mgKOH / g, hydroxyl value = 45 mgKOH / g), KE-100 (hydrogenated rosin ester resin, acid value = 6 mgKOH / g, hydroxyl value = 0 mgKOH / g), KE-311 (hydrogenated rosin ester resin, acid value = 7 mgKOH / g, hydroxyl value = 0 mgKOH / g), etc. manufactured by Arakawa Chemical Industries, Ltd. can be mentioned.

[0013] (Mixing ratio) The rubber composition of the present invention is characterized in that 5 to 120 parts by mass of a rosin ester resin having an acid value of 30 mgKOH / g or less and being hydrogenated is blended with 100 parts by mass of a diene rubber composed only of styrene-butadiene copolymer rubber. When the blending amount of the rosin ester resin is less than 5 parts by mass, the blending amount is too small to exhibit the effects of the present invention. Conversely, when it exceeds 120 parts by mass, the breaking strength decreases. The compounding amount of the rosin ester resin is preferably 15 to 110 parts by mass, more preferably 25 to 100 parts by mass, based on 100 parts by mass of the diene rubber.

[0014] From the viewpoint of further improving the effects of the present invention, the rubber composition for tires of the present invention preferably contains silica having a nitrogen adsorption specific surface area (N2SA) of 100 to 300 m 2 / g. The nitrogen adsorption specific surface area (N2SA) is more preferably 120 to 260 m 2 / g. Further, the compounding amount of the silica is preferably 50 to 250 parts by mass, more preferably 70 to 200 parts by mass, based on 100 parts by mass of the diene rubber. The nitrogen adsorption specific surface area (N2SA) of the silica is a value determined in accordance with JIS K6217-2.

[0015] From the viewpoint of further improving the effects of the present invention, the rubber composition for tires of the present invention preferably contains aluminum hydroxide. The compounding amount of the aluminum hydroxide is preferably 10 parts by mass or more, more preferably 15 to 60 parts by mass, based on 100 parts by mass of the diene rubber.

[0016] Further, the rubber composition for tires of the present invention can contain a silane coupling agent. From the viewpoint of high reactivity, a silane coupling agent having a mercapto group is preferable as the silane coupling agent. The compounding amount of the silane coupling agent is preferably 2.5 to 30% by mass, more preferably 5 to 12% by mass, based on the silica.

[0017] (Other components) In the rubber composition for tires according to the present invention, in addition to the above-described components, vulcanizing or crosslinking agents; vulcanization or crosslinking accelerators; zinc oxide; various fillers such as clay, talc, and calcium carbonate; antioxidants; plasticizers and other various additives generally blended in rubber compositions can be blended. Such additives can be kneaded by a general method to form a composition and used for vulcanization or crosslinking. The blending amounts of these additives can also be set to conventional general blending amounts as long as they do not contravene the object of the present invention.

[0018] Since the rubber composition for tires of the present invention can maintain or improve wear resistance and improve wet grip performance, it can be suitably used for the tread of a tire, particularly the cap tread, preferably the tread of a racing tire, particularly the cap tread. Further, the tire of the present invention is preferably a pneumatic tire and can be filled with an inert gas such as air or nitrogen and other gases.

Examples

[0019] Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

[0020] Standard Example 1, Examples 1 to 7, and Comparative Examples 1 to 4 Preparation of Samples In the formulation (parts by mass) shown in Table 1, the components excluding the vulcanization accelerator and sulfur were kneaded in a 1.7-liter sealed Banbury mixer for 5 minutes, the rubber was discharged outside the mixer and cooled to room temperature. Next, the rubber was put back into the same mixer, the vulcanization accelerator and sulfur were added, and further kneaded to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized in a predetermined mold at 160 ° C for 20 minutes to obtain a vulcanized rubber test piece, and the physical properties of the vulcanized rubber test piece were measured by the test methods shown below.

[0021] Breaking strength: In accordance with JIS K6251, a No. 3 dumbbell-shaped sample piece was punched out from the above vulcanized rubber test piece, and a tensile test was conducted at a tensile speed of 500 mm / min to measure the elongation at break (%). The results were expressed as an index with the value of Standard Example 1 taken as 100. The larger this index, the better the breaking strength and the wear resistance. Wet grip performance: Based on JIS K6394, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., tanδ(0°C) was measured under the conditions of initial strain = 10%, amplitude = ±2%, and frequency = 20 Hz, and this value was used to evaluate the wet grip performance. The results were expressed as an index with Standard Example 1 taken as 100. The larger the index, the better the wet grip performance. The results are shown together in Table 1.

[0022]

Table 1

[0023] *1: SBR (Nipol NS522 manufactured by ZS Elastomer Co., Ltd., oil extension amount = 37.5 parts by mass based on 100 parts by mass of SBR) *2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.) *3: Silica-1 (Ultrasil 7000GR (N2SA 171m 2 / g) manufactured by Evonik) *4: Silica-2 (Zeosil 1085GR (N2SA 86m 2 / g) manufactured by Solvay) *5: Carbon black (Seast 9 manufactured by Tokai Carbon Co., Ltd.) *6: Aluminum hydroxide (BF013 manufactured by Nippon Light Metal Co., Ltd.) *7: Resin-1 (Gum rosin WW, unhydrogenated rosin resin, acid value 170 mgKOH / g, hydroxyl value 0 mgKOH / g manufactured by Arakawa Chemical Industries, Ltd.) *8: Resin-2 (Alcon P-90, hydrogenated petroleum resin, acid value 0 mgKOH / g, hydroxyl value 0 mgKOH / g manufactured by Arakawa Chemical Industries, Ltd.) *9: Resin - 3 (Ester Gum 105 manufactured by Arakawa Chemical Industries, Ltd., unhydrogenated rosin ester resin, acid value 14 mgKOH / g, hydroxyl value 0 mgKOH / g) *10: Resin - 4 (KR - 140 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin resin, acid value 147 mgKOH / g, hydroxyl value 0 mgKOH / g) *11: Resin - 5 (KE - 359 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 13 mg KOH / g, hydroxyl value 45 mgKOH / g) *12: Resin - 6 (KE - 100 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 6 mg KOH / g, hydroxyl value 0 mgKOH / g) *13: Resin - 7 (KE - 311 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 7 mg KOH / g, hydroxyl value 0 mgKOH / g) *14: Silane Coupling Agent - 1 (Si69 manufactured by Evonik, bis(3 - triethoxysilylpropyl)tetrasulfide) *15: Silane Coupling Agent - 2: NXT - Z45 manufactured by Momentive, silane coupling agent with mercapto group) *16: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu KK) *17: Stearic Acid (Bead Stearic Acid YR manufactured by NOF Corporation) *18: Zinc Oxide (Zinc Oxide Type 3 manufactured by Shoindo Chemical Industry Co., Ltd.) *19: Antioxidant (6PPD manufactured by Flexsys) *20: Vulcanization Accelerator - 1 (Sunceler D - G manufactured by Sanshin Chemical Industry Co., Ltd.) *21: Vulcanization Accelerator - 2 (Nocceler CZ - G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *22: Sulfur (Fine Powder Sulfur for Cinnabar Ink manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0024] From the results in Table 1, it can be seen that the rubber composition for tires of the examples contains 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less with respect to 100 parts by mass of the diene rubber composed only of styrene-butadiene copolymer rubber. Therefore, compared with Standard Example 1, the abrasion resistance is maintained or improved, and the wet grip performance is improved. On the other hand, Comparative Example 1 uses a hydrogenated petroleum resin, so the breaking strength decreased and the abrasion resistance deteriorated. Comparative Example 2 uses a non-hydrogenated rosin ester resin, so the abrasion resistance and wet grip performance decreased. Comparative Example 3 uses a rosin ester resin whose acid value exceeds the upper limit specified in the present invention, so the wet grip performance decreased. Comparative Example 4 is an example in which butadiene rubber (BR) is blended, so the wet grip performance decreased.

[0025] The present disclosure includes the following inventions. Invention [1]: A rubber composition for tires, characterized in that 1 to 100 parts by mass of a rosin ester resin having an acid value of less than 30 mgKOH / g is blended with respect to 100 parts by mass of a diene rubber. Invention [2]: The rubber composition for tires according to Invention 1, characterized in that the hydroxyl value of the rosin ester resin is 50 mgKOH / g or less. Invention [3]: The rubber composition for tires according to Invention 1 or 2, characterized in that 50 to 250 parts by mass of silica having a nitrogen adsorption specific surface area (N2SA) of 100 to 300 m 2 / g is blended with respect to 100 parts by mass of the diene rubber. Invention [4]: The rubber composition for tires according to any one of Inventions 1 to 3, characterized in that 10 parts by mass or more of aluminum hydroxide is further blended with respect to 100 parts by mass of the diene rubber. Invention [5]: The rubber composition for tires according to Invention 3, characterized in that 2.5 to 30% by mass of a silane coupling agent having a mercapto group is further blended with respect to the silica. Invention [6]: A tire using the rubber composition for tires according to any one of Inventions 1 to 5 for a cap tread.

Claims

1. A rubber composition for tires, characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less is blended with 100 parts by mass of a diene rubber consisting only of a styrene-butadiene copolymer rubber.

2. The rubber composition for tires according to claim 1, wherein the hydroxyl value of the rosin ester resin is 50 mgKOH / g or less.

3. Based on 100 parts by mass of the diene rubber, further 50 to 250 parts by mass of silica having a nitrogen adsorption specific surface area (N ２ SA) of 100 to 300 m ２ / g is blended. The rubber composition for tires according to claim 1, characterized in that.

4. The rubber composition for tires according to claim 1, further characterized in that 10 parts by mass or more of aluminum hydroxide is blended with 100 parts by mass of the diene rubber.

5. The rubber composition for tires according to claim 3, further characterized in that 2.5 to 30% by mass of a silane coupling agent having a mercapto group is blended with respect to the silica.

6. A tire using the rubber composition for tires according to claim 1 for a cap tread.

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