Rubber composition for tires and tires

Abstract

In general, tires are required to have a wide range of performance characteristics, but among them, they are required to simultaneously satisfy wet grip performance and wear resistance, a requirement that also exists for racing tires for circuit driving. [Solution] The above problem was solved by providing a rubber composition for tires, which is characterized by blending 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less with 100 parts by mass of a diene rubber consisting only of a styrene-butadiene copolymer rubber.

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 that can maintain or improve abrasion resistance and improve wet grip performance, and a tire using the same. [Background technology]

[0002] In general, pneumatic tires for racing are prepared for dry road running and wet road running, and the optimum tire is selected according to the weather and road surface conditions during the running. Here, for racing tires for running on wet roads, a method such as compounding a large amount of filler or resin with a high specific surface area is used to improve wet grip performance, but the conventional technology has a problem of reduced wear resistance.

[0003] Note that, although techniques for blending a rosin-based resin into a rubber composition for tires are found in Patent Documents 1 to 3, etc., the following Patent Documents do not disclose or suggest at all the technical idea of ​​maintaining or improving abrasion resistance and improving wet grip performance by blending a specific amount of hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less with a diene rubber consisting only of a styrene-butadiene copolymer rubber described below. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-193444 A [Patent Document 2] Patent No. 7151083 [Patent Document 3] Patent Publication No. 2021-95465 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a rubber composition for tires that can maintain or improve abrasion resistance and improve wet grip performance, and a tire using the same. [Means for solving the problem]

[0006] 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 a hydrogenated rosin ester resin having an acid value within a specific range with a diene rubber consisting only of a styrene-butadiene copolymer rubber, and have thus completed the present invention.

[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 consisting only of a styrene-butadiene copolymer rubber. Effect 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 consisting only of a styrene-butadiene copolymer rubber. Therefore, it is possible to provide a rubber composition for tires that can maintain or improve abrasion 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, and therefore has a higher compatibility with styrene-butadiene copolymer rubber than resins having a higher acid value, and does not show excessive reactivity when a vulcanization accelerator is used, so that the decrease in breaking strength and hardness can be suppressed. In addition, the rosin ester resin is hydrogenated, which exerts the effect of increasing compatibility with styrene-butadiene copolymer rubber. It is presumed that this makes it possible to provide a rubber composition for tires that can maintain or improve abrasion resistance and improve wet grip performance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will now be described in further detail.

[0011] (Diene rubber) The diene rubber used in the present invention is composed of only styrene-butadiene copolymer rubber (SBR). There are no particular limitations on the molecular weight or microstructure of the SBR, and it may be terminally modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl, or the like, or may be epoxidized. The weight average molecular weight (Mw) of SBR is not particularly limited, but in order to obtain better effects of the present invention, it is preferably from 100,000 to 5,000,000, more preferably from 200,000 to 3,000,000, and even more preferably from 300,000 to 2,000,000. In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene by gel permeation chromatography (GPC).

[0012] (rosin ester resin) The rosin ester resin used in the present invention can be one obtained by reacting a raw material rosin ester such as gum rosin, tall oil rosin, or wood rosin with an alcohol and polymerizing the resulting mixture in the presence of a catalyst. The esterification reaction and polymerization reaction may be carried out under known conditions. The resulting rosin ester resin may be purified as necessary, and the color of the purified rosin ester resin is usually 10 or less on the Gardner color scale. 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, compatibility with SBR is increased, improving wet grip performance, and when a vulcanization accelerator is used, excessive reactivity is not exhibited, 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. The rosin ester resin used in the present invention is hydrogenated. Hydrogenation enhances compatibility with styrene-butadiene copolymer rubber, thereby improving the breaking strength. Hydrogenation is preferably carried out until the Hazen color number (JIS K0071-1) of the rosin ester resin becomes 200 or less. In order to improve 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, compatibility with SBR is improved, and wet grip performance can be further improved. From the viewpoint of improving the effects of the present invention, the rosin ester resin used in the present invention preferably has a weight average molecular weight of 200 to 1800, and more preferably 300 to 1500, a glass transition temperature of preferably 20 to 100°C, and more preferably 30 to 90, and a softening point (JIS K6220-1) of preferably 60 to 150°C, and more preferably 70 to 140. The rosin ester resin used in the present invention may be a commercially available product, and examples thereof include KE-359 (hydrogenated rosin ester resin, acid value = 13 mg KOH / g, hydroxyl value = 45 mg KOH / g), KE-100 (hydrogenated rosin ester resin, acid value = 6 mg KOH / g, hydroxyl value = 0 mg KOH / g), and KE-311 (hydrogenated rosin ester resin, acid value = 7 mg KOH / g, hydroxyl value = 0 mg KOH / g), all of which are manufactured by Arakawa Chemical Industries, Ltd.

[0013] (Mixing ratio) The rubber composition 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 consisting only of a styrene-butadiene copolymer rubber. If the amount of the rosin ester resin is less than 5 parts by mass, the amount is too small to achieve the effects of the present invention, whereas if it exceeds 120 parts by mass, the breaking strength decreases. The amount of the rosin ester resin to be mixed is preferably from 15 to 110 parts by mass, and more preferably from 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 a tire of the present invention has a nitrogen adsorption specific surface area (N 2 SA) is 100~300m 2 It is preferable to incorporate silica having a content of 0.1 to 1.0 g / g. The nitrogen adsorption specific surface area (N 2 SA) is 120~260m 2 It is even more preferred that the weight ratio is / g. The amount of silica to be blended 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. 2 SA) is a value determined in accordance with JIS K6217-2.

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

[0016] The rubber composition for tires of the present invention may further contain a silane coupling agent. As the silane coupling agent, a silane coupling agent having a mercapto group is preferred due to its high reactivity. The 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 ingredients) In addition to the above-mentioned components, the rubber composition for tires of the present invention may contain various additives that are generally compounded in rubber compositions, such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, zinc oxide, various fillers such as clay, talc, and calcium carbonate, antioxidants, and plasticizers, and these additives can be kneaded by a general method to form a composition, which can be used for vulcanization or crosslinking. The amounts of these additives may be conventional amounts, so long as they do not go against the object of the present invention.

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

[0019] The present invention will be further described below 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 Sample preparation In the formulation (parts by mass) shown in Table 1, the components other than 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 at room temperature. The rubber was then placed back into the mixer, and the vulcanization accelerator and sulfur were added and further kneaded to obtain a rubber composition. The obtained rubber composition was then press-vulcanized in a specified 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: According to JIS K6251, a No. 3 dumbbell-shaped sample piece was punched out from the vulcanized rubber test piece, and a tensile test was carried out at a tensile speed of 500 mm / min to measure the breaking elongation (%). The results were expressed as an index, with the value of Standard Example 1 being 100. A larger index indicates better breaking strength and better abrasion resistance. Wet grip performance: Based on JIS K6394, tan δ (0°C) was measured using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under the conditions of initial strain = 10%, amplitude = ±2%, and frequency = 20Hz, and the wet grip performance was evaluated based on this value. The results were expressed as an index, with standard example 1 being 100. The larger the index, the better the wet grip performance. The results are also shown in Table 1.

[0022] [Table 1]

[0023] *1: SBR (Nipol NS522 manufactured by ZS Elastomers Co., Ltd., oil extension amount = 37.5 parts by weight per 100 parts by weight of SBR) *2: BR (Nipol BR1220 manufactured by Zeon Corporation) *3: Silica-1 (Evonik Ultrasil 7000GR(N 2 SA 171m 2 / g) *4: Silica-2 (Solvay Zeosil 1085GR(N 2 SA 86m 2 / g) *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 (Arakawa Chemical Industries, Ltd. Gum Rosin WW, unhydrogenated rosin resin, acid value 170 mg KOH / g, hydroxyl value 0 mg KOH / g) *8: Resin-2 (Arcon P-90 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated petroleum resin, acid value 0 mg KOH / g, hydroxyl value 0 mg KOH / g) *9: Resin-3 (Ester Gum 105 manufactured by Arakawa Chemical Industries, Ltd., unhydrogenated rosin ester resin, acid value 14 mg KOH / g, hydroxyl value 0 mg KOH / g) *10: Resin-4 (KR-140 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin resin, acid value 147 mg KOH / g, hydroxyl value 0 mg KOH / g) *11: Resin-5 (KE-359 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 13mg KOH / g, hydroxyl value 45mg KOH / g) *12: Resin-6 (KE-100 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 6mg KOH / g hydroxyl value 0mg KOH / g) *13: Resin-7 (KE-311 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 7mg KOH / g hydroxyl value 0mg KOH / g) *14: Silane coupling agent-1 (Evonik Si69, bis(3-triethoxysilylpropyl)tetrasulfide) *15: Silane coupling agent-2: Momentive's NXT-Z45, a silane coupling agent with a mercapto group) *16: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu K.K.) *17: Stearic acid (Beads Stearic Acid YR manufactured by NOF Corporation) *18: Zinc oxide (3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd.) *19: Anti-aging agent (Flexis 6PPD) *20: Vulcanization accelerator-1 (Sansera DG manufactured by Sanshin Chemical Industry Co., Ltd.) *21: Vulcanization accelerator-2 (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *22: Sulfur (Kinka-in oil-filled fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0024] The results in Table 1 show that the rubber composition for tires of the embodiment contains 100 parts by mass of diene rubber consisting only of styrene-butadiene copolymer rubber and 5 to 120 parts by mass of hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less, and therefore the abrasion resistance is maintained or improved and the wet grip performance is improved compared to Reference Example 1. In contrast, Comparative Example 1 was an example in which a hydrogenated petroleum resin was used, and therefore the breaking strength was reduced and the abrasion resistance was deteriorated. Comparative Example 2 is an example in which a non-hydrogenated rosin ester resin was used, and therefore the abrasion resistance and wet grip performance were deteriorated. Comparative Example 3 is an example in which a rosin ester resin having an acid value exceeding the upper limit specified in the present invention was used, and therefore the wet grip performance was deteriorated. Comparative Example 4 is an example in which butadiene rubber (BR) was compounded, and therefore the wet grip performance was deteriorated.

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

Claims

1. A rubber composition for tires 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 and a hydroxyl value of 50 mgKOH / g or less is blended with 100 parts by mass of a diene rubber consisting only of a styrene-butadiene copolymer rubber.

2. Further, a nitrogen adsorption specific surface area (N ２ SA) is 100 to 300 m ２ 2. The rubber composition for tires according to claim 1, further comprising 50 to 250 parts by mass of silica having a molecular weight of 1 / g.

3. 2. The rubber composition for tires according to claim 1, further comprising 10 parts by mass or more of aluminum hydroxide per 100 parts by mass of the diene rubber.

4. 3. The rubber composition for tires according to claim 2, further comprising 2.5 to 30% by mass of a silane coupling agent having a mercapto group blended with respect to the silica.

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

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