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 dry grip performance, warm-up performance and steering stability.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, and 50 to 200 pts.mass of carbon black having a nitrogen adsorption specific surface area (N2SA) of 100 to 500 m2 / g, 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 handling stability and improving both dry grip performance and warm-up performance, and a tire using the same.

Background Art

[0002] Generally, for competitive pneumatic tires, 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, for competitive tires for dry road surface driving, a method of blending a large amount of small particle size carbon black or resin is known in order to improve the grip performance (dry grip performance) on the dry road surface. However, these blending methods have a problem that it takes time until the dry grip performance is activated, and the warm-up performance deteriorates. On the other hand, the blending of softening agents such as low softening point resins and oils has also been studied, but none of these methods can achieve both dry grip performance and handling stability.

[0003] As a technique of blending a rosin resin into a rubber composition for tires, it can be seen in Patent Documents 1 to 3 below. However, for a diene rubber composed 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 and a carbon black having a specific specific surface area are blended in a specific amount, and the technical idea of maintaining or improving handling stability and improving both dry grip performance and warm-up performance is not disclosed or suggested at all.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] Accordingly, an object of the present invention is to provide a rubber composition for tires that can maintain or improve handling stability and improve both dry grip performance and warm-up performance, and a tire using the same. [Means for Solving the Problems]

[0006] As a result of intensive research, the present inventors have found that by blending a hydrogenated rosin ester resin having an acid value within a specific range and carbon black having a specific specific surface area 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 and 50 to 200 parts by mass of carbon black having a nitrogen adsorption specific surface area (N2SA) of 100 to 500 m 2 / g are 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 contains 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less and 50 to 200 parts by mass of carbon black having a nitrogen adsorption specific surface area (N2SA) of 100 to 500 m 2Since it is characterized in that 50 to 200 parts by mass of carbon black per g is blended, it is possible to provide a rubber composition for a tire that can maintain or improve handling stability and improve both dry grip performance and warm-up 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, compared with a resin having a higher acid value, its compatibility with styrene-butadiene copolymer rubber is enhanced, and when a vulcanization accelerator is used, it does not show excessive reactivity. For these reasons, it is possible to maintain or improve handling stability and simultaneously enhance dry grip performance and warm-up performance. In addition, since the rosin ester resin is hydrogenated, it exhibits the effect of enhancing compatibility with styrene-butadiene copolymer rubber.

Mode for Carrying Out the Invention

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

[0011] (Diene-based rubber) The diene-based 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 an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or may be epoxidized. The weight average molecular weight (Mw) of SBR is not particularly limited, but for reasons such 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. Moreover, the SBR used in the present invention preferably has a styrene content of less than 35% by mass, more preferably 30% by mass or less. By setting the styrene content as described above, the polarity of the SBR is lowered, and the compatibility with the rosin ester resin can be further enhanced.

[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 the 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. By having an acid value of 30 mgKOH / g or less, the compatibility with SBR is enhanced, and the above-described effects can be exhibited. In the present invention, the acid value is more preferably 20 mgKOH / g or less. Moreover, the rosin ester resin used in the present invention is hydrogenated. Hydrogenation exhibits the effect of improving the breaking strength because the compatibility with styrene-butadiene copolymer rubber is enhanced. Hydrogenation is preferably carried out until the Hazen unit color number (JIS K0071-1) of the rosin ester resin becomes 200 or less. Moreover, 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. By having a hydroxyl value of 50 mgKOH / g or less, the compatibility with SBR is enhanced, and the dry grip performance can be further improved. From the perspective 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 °C. The softening point (JIS K6220-1) is preferably 60 to 150 °C, more preferably 70 to 140 °C. 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, based on 100 parts by mass of a diene rubber consisting only of a styrene-butadiene copolymer rubber, 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less and a carbon black having a nitrogen adsorption specific surface area (N2SA) of 100 to 500 m 2 / g are blended in an amount of 50 to 200 parts by mass. When the blending amount of the rosin ester resin is less than 5 parts by mass, the blending amount is too small to achieve the effects of the present invention. Conversely, when it exceeds 120 parts by mass, the hardness (100 °C) decreases. The blending amount of the rosin ester resin is preferably 5 to 120 parts by mass, more preferably 15 to 110 parts by mass, and particularly preferably 25 to 100 parts by mass, based on 100 parts by mass of the diene rubber. Also, when the blending amount of the carbon black is less than 50 parts by mass, the hardness (100 °C) decreases. Conversely, when it exceeds 200 parts by mass, the hardness (20 °C) decreases. The blending amount of the carbon black is preferably 50 to 200 parts by mass, more preferably 70 to 180 parts by mass, based on 100 parts by mass of the diene rubber. The nitrogen adsorption specific surface area (N2SA) range of the carbon black is an effective range for achieving the effects of the present invention. A more preferable nitrogen adsorption specific surface area (N2SA) range is 120 to 400 m 2 / g. The nitrogen adsorption specific surface area (N2SA) is a value determined in accordance with JIS K6217-2.

[0014] (Liquid aromatic vinyl-conjugated diene rubber) The rubber composition for tires of the present invention preferably contains a liquid aromatic vinyl-conjugated diene rubber having a glass transition temperature (Tg) of -40°C or higher. By blending such a liquid aromatic vinyl-conjugated diene rubber, the glass transition temperature (Tg) of the rubber composition can be increased, and the dry grip performance can be enhanced. In addition, the liquid aromatic vinyl-conjugated diene rubber is compatible with SBR and can enhance the dispersibility of the rosin ester resin used in the present invention, thereby enhancing the effects of the present invention. As the liquid aromatic vinyl-conjugated diene rubber, a liquid styrene-butadiene copolymer (liquid SBR) is preferable. The liquid SBR has a weight average molecular weight of 2000 to 40000, preferably 3000 to 20000. The glass transition temperature of the liquid SBR is -40°C or higher as described above, and more preferably -20°C to -5°C. Commercial liquid SBR can be used, such as RICON 100 manufactured by Cray Valley and L-SBR 820 manufactured by Kuraray Co., Ltd. In the present invention, Tg refers to the temperature at the midpoint of the transition region measured by a thermogram under the condition of a heating rate of 20°C / min by differential scanning calorimetry (DSC). The liquid aromatic vinyl-conjugated diene rubber used in the present invention is liquid at 23°C. Therefore, it is distinguished from the diene rubber that is solid at this temperature. In addition, the blending amount of the liquid aromatic vinyl-conjugated diene rubber is preferably 5 to 50 parts by mass, more preferably 10 to 45 parts by mass, based on 100 parts by mass of the diene rubber.

[0015] (Other components) In the rubber composition for tires of 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 compounded in rubber compositions can be compounded. Such additives can be kneaded by a general method to form a composition and used for vulcanization or crosslinking. The compounding amounts of these additives can also be set to conventional general compounding amounts as long as they do not conflict with the object of the present invention.

[0016] Since the rubber composition for tires of the present invention can maintain or improve handling stability and improve both dry grip performance and warm-up performance, it can be suitably used for the tread of tires, particularly the cap tread, preferably the tread of racing tires, 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, nitrogen, or other gases.

Examples

[0017] 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.

[0018] Standard Example 1, Examples 1 to 6, and Comparative Examples 1 to 5 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 closed Banbury mixer for 5 minutes, and 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 kneading was further performed to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized at 160 ° C. for 20 minutes in a predetermined mold 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.

[0019] Warm-up performance: The hardness was measured at 20 ° C. in accordance with JIS K6253, and this value was used to evaluate the dry grip performance. The results were expressed as an index with the value of Standard Example 1 being 100. The smaller the index, the better the warm-up performance. Handling stability: The hardness was measured at 100 °C in accordance with JIS K6253, and this value was used to evaluate the handling stability. The results were shown as an index with the value of Standard Example 1 being 100. The larger the index, the higher the hardness at 100 °C and the better the handling stability. Dry grip performance: Based on JIS K6394, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., tanδ(100 °C) was measured under the conditions of initial strain = 10%, amplitude = ±2%, and frequency = 20 Hz, and this value was used to evaluate the dry grip performance. The results were shown as an index with the value of Standard Example 1 being 100. The larger the index, the better the dry grip performance. The results are shown together in Table 1.

[0020]

Table 1

[0021] *1: SBR-1 (Nipol 1739 manufactured by Zeon Corporation, Japan, styrene content = 40% by mass, oil extension amount = 37.5 parts by mass based on 100 parts by mass of SBR) *2: SBR-2 (Nipol 1723 manufactured by Zeon Corporation, Japan, styrene content = 23.5% by mass, oil extension amount = 37.5 parts by mass based on 100 parts by mass of SBR) *3: BR (Nipol BR1220 manufactured by Zeon Corporation, Japan) *4: Carbon black - 1 (Seast 9 manufactured by Tokai Carbon Co., Ltd. (N2SA 142m 2 / g)) *5: Carbon black - 2 (Shoublack N339 (N2SA 94m manufactured by Cabot Japan Ltd. 2 / g)) *6: Resin - 1 (Gum rosin WW manufactured by Arakawa Chemical Industries, Ltd., unhydrogenated rosin resin, acid value 170 mgKOH / g, hydroxyl value 0 mgKOH / g) *7: Resin - 2 (Alcon P - 90 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated petroleum resin, acid value 0 mgKOH / g, hydroxyl value 0 mgKOH / g) *8: 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) *9: Resin - 4 (KR - 140 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin resin, acid value 147 mgKOH / g, hydroxyl value 0 mgKOH / g) *10: 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) *11: 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) *12: 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) *13: Liquid SBR (RICON 100 manufactured by Cray Valley, weight - average molecular weight = 6400, Tg = - 15°C) *14: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu K.K.) *15: Stearic acid (Bead Stearic Acid YR manufactured by NOF Corporation) *16: Zinc oxide (Zinc Oxide No. 3 manufactured by Sho - do Chemical Industry Co., Ltd.) *17: Antioxidant (6PPD manufactured by Flexsys) *18: Vulcanization accelerator (Nocceler CZ - G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *19: Sulfur (Fine Powder Sulfur for Stamp Ink manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0022] From the results in Table 1, the rubber composition for tires of the examples contains, per 100 parts by mass of the diene - based rubber consisting only of styrene - butadiene copolymer rubber, 5 to 120 parts by mass of a rosin ester resin having an acid value of 30 mgKOH / g or less and being hydrogenated, and 50 to 200 parts by mass of carbon black having a nitrogen adsorption specific surface area (N2SA) of 100 to 500 m 2 / g. It can be seen that, compared with Standard Example 1, the handling stability is maintained or improved, and the dry grip performance and warm - up performance are simultaneously improved. In contrast, Comparative Example 1 used a hydrogenated petroleum resin, resulting in deteriorated handling stability and dry grip performance. Comparative Example 2 used a non-hydrogenated rosin ester resin, resulting in deteriorated warm-up performance. Comparative Example 3 used a rosin ester resin with an acid value exceeding the upper limit defined in the present invention, resulting in deteriorated warm-up performance. Comparative Example 4 had a nitrogen adsorption specific surface area (N2SA) of carbon black outside the scope of the present invention, resulting in deteriorated handling stability and dry grip performance. Comparative Example 5 was an example in which butadiene rubber (BR) was compounded, resulting in deteriorated handling stability and dry grip performance.

[0023] The present disclosure includes the following inventions. Invention [1]: Based on 100 parts by mass of a diene rubber consisting only of a styrene-butadiene copolymer rubber, 5 to 120 parts by mass of a rosin ester resin having an acid value of 30 mgKOH / g or less and being hydrogenated, and a carbon black having a nitrogen adsorption specific surface area (N2SA) of 100 to 500 m 2 / g are compounded in an amount of 50 to 200 parts by mass, a rubber composition for tires. Invention [2]: The rubber composition for tires according to Invention 1, wherein 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, wherein the styrene-butadiene copolymer rubber has a styrene content of less than 35% by mass. Invention [4]: The rubber composition for tires according to any one of Inventions 1 to 3, further comprising a liquid aromatic vinyl-conjugated diene rubber having a glass transition temperature (Tg) of -40°C or higher based on 100 parts by mass of the diene rubber. Invention [5]: A tire using the rubber composition for tires according to any one of Inventions 1 to 4 for a cap tread.

Claims

1. Based on 100 parts by mass of a diene rubber consisting only of a styrene-butadiene copolymer rubber, 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mg KOH / g or less, and a nitrogen adsorption specific surface area (N ２ SA) of 100 to 500 m ２ / g of carbon black is compounded in an amount of 50 to 200 parts by mass. A rubber composition for a tire, characterized by the above.

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. The rubber composition for tires according to claim 1, wherein the styrene-butadiene copolymer rubber has a styrene content of less than 35% by mass.

4. The rubber composition for tires according to claim 1, further comprising 5 to 50 parts by mass of a liquid aromatic vinyl-conjugated diene rubber having a glass transition temperature (Tg) of -40°C or higher, based on 100 parts by mass of the diene rubber.

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

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