JP7251563B2 - Tire rubber composition and tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition for tires and a tire, and more particularly, a rubber composition for tires capable of enhancing dry grip performance and graining performance, suppressing the temperature dependence of hardness, and improving heat sag performance. and a tire using the same.

In general, the performance required for pneumatic tires for competitions is diverse, and in addition to excellent steering stability (dry grip performance) on dry road surfaces during high-speed driving, , to suppress changes in tire performance such as heat sag.
Therefore, in order to improve the dry grip performance, for example, conventionally, a large amount of carbon black having a high specific surface area, a tackifying resin, and a plasticizer are blended.
However, with the above measures, the graining performance (wear resistance and grip performance at low temperatures) deteriorates, and the temperature dependence of hardness occurs, resulting in deterioration of heat sag performance, which is a cause of reduced time in competitions. becomes.

In Patent Document 1 below, (A) 100 parts by mass of a diene-based rubber containing an aromatic vinyl-conjugated diene-based rubber having a glass transition temperature (Tg) of −35° C. or higher is added to (B) a nitrogen adsorption specific surface area ( 50 to 200 parts by mass of carbon black having a N ₂ SA) of 100 to 400 m ² /g and a DBP absorption of 100 to 200 cm ³ /100 g, and (C) distyrenated phenol or tristyrenated phenol as main components A rubber composition for a tire tread is disclosed, which is characterized by blending 0.5 to 20 parts by mass of a styrenated phenol compound.
However, the technique disclosed in Patent Document 1 cannot satisfy all of dry grip performance, graining performance and heat sag performance.

JP 2016-113482 A

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rubber composition for tires capable of enhancing dry grip performance and graining performance, suppressing the temperature dependence of hardness and improving heat sagging performance, and a tire using the same. be.

As a result of extensive research, the inventors of the present invention have found that by blending a specific amount of carbon black having specific characteristics with a specific composition of diene rubber and further blending a specific amount of a styrenated phenol compound, , found that the above problems can be solved, and completed the present invention.

That is, the present invention has a nitrogen adsorption specific surface area N ₂ SA of 100 to 500 m ² /g with respect to 100 parts by mass of a diene rubber containing a styrene-butadiene copolymer rubber having a styrene content of 30% by mass or more, and 50 to 200 masses of carbon black having a ratio of N ₂ SA/IA, which is the ratio of the nitrogen adsorption specific surface area N ₂ SA (unit m ² /g) to the iodine adsorption amount IA (unit mg/g), is 0.90 to 1.03 part, 5 to 50 parts by mass of a styrenated phenol compound represented by the following structural formula (1), and 20 parts by mass or more of a tackifying resin, and the amount of the styrenated phenol compound is the tackifying Provided is a rubber composition for tires characterized by containing 15% by mass or more of the resin.

(In Structural Formula (1), n is 2 or 3)

The rubber composition for tires of the present invention is obtained by blending a specific amount of carbon black having specific properties with a diene rubber having a specific composition, and further blending a specific amount of a styrenated phenol compound. Thus, it is possible to provide a rubber composition for tires capable of enhancing dry grip performance and graining performance, suppressing the temperature dependence of hardness and improving heat sagging performance, and a tire using the same.

The present invention will now be described in more detail.

(Diene rubber)
The diene rubber used in the present invention contains styrene-butadiene copolymer rubber (SBR) as an essential component. When the total amount of the diene rubber used in the present invention is 100 parts by mass, the amount of SBR compounded may be determined in consideration of various conditions such as temperature and weather in the case of competition use, for example. For example, it can be 70 parts by mass or more, preferably 85 parts by mass or more, and more preferably 100 parts by mass. In addition to SBR, the present invention can use any diene rubber that can be blended in a normal rubber composition, such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR ), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene-diene terpolymer (EPDM), and the like. These may be used alone or in combination of two or more. Further, its molecular weight and microstructure are not particularly limited, and it may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or epoxidized.

Moreover, the SBR used in the present invention preferably has a styrene content of 30% by mass or more. By satisfying such a styrene content, the glass transition temperature (Tg) of SBR can be increased, and the dry grip performance can be enhanced. A more preferable styrene content is 33 to 50% by mass.

(Carbon black)
The carbon black used in the present _invention has a nitrogen adsorption specific surface area N ₂ SA of 100 to 500 ^{m 2} /g. ), the ratio of N ₂ SA/IA is 0.90 to 1.03 (hereinafter sometimes referred to as specific carbon black). Carbon black satisfying this N ₂ SA/IA can be said to have a large number of functional groups present on the surface and high surface activity. Carbon black with high surface activity has a high interaction with the OH group contained in the styrenated phenol compound described below, improves dry grip performance and graining performance, suppresses the temperature dependence of hardness, and is heat resistant. Sagging performance can also be improved.

In the specific carbon black used in the present invention, the N ₂ SA is preferably 150 to 400 m ² /g from the viewpoint of further enhancing the above effects, and the N ₂ SA/IA is 0.92. It is preferably ~1.01, more preferably 0.93 to 1.00. Also, the IA is preferably 130 to 500 mg/g, more preferably 150 to 470 mg/g.
N ₂ SA shall be measured according to JIS K6217-2, and IA shall be measured according to JIS K6217-1.

(Styrenated phenol compound)
The styrenated phenol compound used in the present invention can be represented by the following structural formula (1). The styrenated phenol compound used in the present invention has the function of interacting with diene rubber to increase tan δ and improve dry grip performance.

In the styrenated phenol compound represented by Structural Formula (1), n is 2 or 3. That is, the styrenated phenol compound used in the present invention is a distyrenated phenol where n is 2 or a tristyrenated phenol where n is 3. Mixtures of distyrenated phenolic compounds and tristyrenated phenolic compounds can also be used in the present invention. In the styrenated phenol compound, if the styrene portion in the molecule is small, the interaction with the diene rubber is reduced, making it difficult to obtain the desired effect. From this point of view, it is desirable not to use a monostyrenated phenol compound in which n is 1 in the present invention. The monostyrenated phenol compound may be contained in a trace amount (for example, 0.1% by mass or less based on the total styrenated phenol compound used).
The styrenated phenol compound represented by Structural Formula (1) can be produced by a known production method and is also commercially available. Commercially available products include, for example, SP-24 manufactured by Sanko Co., Ltd. (mainly containing distyrenated phenol), TSP (mainly containing tristyrenated phenol), and the like.

The styrene moiety in the above formula may be a styrene derivative. Examples include α-methylstyrene, o-methylstyrene, 1,3-dimethylstyrene and the like.

(tackifying resin)
The tackifying resin used in the present invention is not particularly limited, but specific examples thereof include phenolic resins (e.g., phenolic resins, phenol-acetylene resins, phenol-formaldehyde resins), coumarone-based resins (e.g., coumarone resins, coumarone-indene resin, coumarone-indene-styrene resin), terpene-based resin (e.g., terpene resin, modified terpene resin (aromatic modified terpene resin, etc.), terpene-phenolic resin), styrene resin, acrylic resin, rosin-based resin (e.g., , rosin, rosin ester, hydrogenated rosin derivative), hydrogenated terpene resin), petroleum resin (e.g., C5 petroleum resin such as dicyclopentazine resin, C9 petroleum resin, alicyclic petroleum resin, C5/C9 polymerized petroleum resins), xylene resins (eg, xylene resins, xylene-acetylene resins, xylene-formaldehyde resins), α-pinene resins, aliphatic saturated hydrocarbon resins, and the like. Among them, one selected from C9 petroleum resins, phenolic resins, coumarone-indene resins, terpene resins, styrene resins, acrylic resins, rosin-based resins and dicyclopentadiene resins because the effects of the present invention are more excellent. It is preferable that it is above.

The softening point of the tackifying resin is preferably 60 to 180° C. for the reason that the effects of the present invention are more excellent.
The softening point is measured according to JIS K6220-1.

(Mixing ratio of rubber composition)
The rubber composition of the present invention contains 50 to 200 parts by mass of a specific carbon black, 5 to 50 parts by mass of a styrenated phenol compound represented by the structural formula (1) with respect to 100 parts by mass of a diene rubber, and a tackifier. 20 parts by mass or more of a resin is blended, and the amount of the styrenated phenol compound is 15% by mass or more with respect to the tackifying resin.
When the content of the specific carbon black is less than 50 parts by mass, the tan δ60° C. decreases, and when it exceeds 200 parts by mass, the strength at break decreases.
If the amount of the styrenated phenol compound is less than 5 parts by mass, the amount is too small to achieve the effects of the present invention.
If the amount of the tackifying resin is less than 20 parts by mass, the tan δ60° C. is lowered.
If the content of the styrenated phenol compound is less than 15% by mass relative to the tackifying resin, the temperature dependency of graining performance and hardness deteriorates.

In the rubber composition of the present invention, the amount of the specific carbon black compounded is preferably 70 to 190 parts by mass, more preferably 90 to 180 parts by mass, per 100 parts by mass of the diene rubber.
The amount of the styrenated phenol compound compounded is preferably 7 to 45 parts by mass, more preferably 10 to 40 parts by mass, per 100 parts by mass of the diene rubber.
The content of the tackifying resin is preferably 25 to 90 parts by mass, more preferably 30 to 80 parts by mass, per 100 parts by mass of the diene rubber.
The content of the styrenated phenol compound is preferably 20 to 80% by mass relative to the tackifying resin.

(Other ingredients)
In addition to the above components, the rubber composition of the present invention includes vulcanizing or cross-linking agents; vulcanizing or cross-linking accelerators; various fillers such as silica, clay, talc and calcium carbonate; anti-aging agents; ; Resin; Various additives generally blended in rubber compositions such as curing agents can be blended. can be used for The blending amount of these additives can also be a conventional general blending amount as long as it does not contradict the object of the present invention.

The rubber composition of the present invention can improve dry grip performance and graining performance, suppress the temperature dependence of hardness, and improve heat sag performance. It can be suitably used for tire treads, particularly cap treads. Moreover, the tire of the present invention is preferably a pneumatic tire, and can be filled with air, an inert gas such as nitrogen, or other gases.

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.

Standard Example, Examples 1-2 and Comparative Examples 1-6
Sample preparation In the formulation (parts by mass) shown in Table 1, the components except for the vulcanization system (vulcanization accelerator, sulfur) were kneaded in a 1.7-liter closed Banbury mixer for 5 minutes, and then discharged out of the mixer. and cooled to room temperature. Subsequently, the composition was placed in the same Banbury mixer again, and the vulcanizing system was added and kneaded to obtain a rubber composition. Next, the obtained rubber composition was press-vulcanized in a predetermined mold at 150° C. for 30 minutes to prepare a vulcanized rubber test piece. The physical properties of the obtained vulcanized rubber test pieces were measured by the following test methods.

tan δ (60 ° C.): According to JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho), under conditions of extension deformation strain rate 10 ± 2%, frequency 20 Hz, temperature 60 ° C., tan δ (60 °C) was measured. The results were indexed with the value of the standard example set to 100. The larger the index, the higher the tan δ and the better the dry grip performance.
M300 (RT)/M300 (60°C): A tensile test was performed at room temperature (RT) or 60°C based on JIS K6251 (using No. 3 dumbbells) to determine the 300% deformation modulus (M300). The results were indexed with the value of the standard example set to 100. The smaller the index, the lower the temperature dependence and the better the heat sag performance.
Brittleness temperature: The brittleness temperature was measured according to the low-temperature impact embrittlement test of JIS K6261 "Vulcanized rubber and thermoplastic rubber-How to determine low-temperature properties". The results were indexed with the value of the standard example set to 100. A smaller index indicates better wear resistance and grip performance at low temperatures.
Breaking strength (RT): Based on JIS K6251, breaking elongation was evaluated at room temperature by a tensile test. The results were indexed with the value of the standard example set to 100. The larger the index, the better the breaking strength, the better the wear resistance, and the better the graining resistance.

Table 1 shows the results.

* 1: SBR1 (Nipol NS522 manufactured by ZS Elastomer Co., Ltd. (styrene content = 39% by mass, oil extension = 37.5 parts by mass for 100 parts by mass of SBR))
* 2: SBR2 (Nipol NS460 manufactured by ZS Elastomer Co., Ltd. (styrene content = 25% by mass, oil extension = 37.5 parts by mass for 100 parts by mass of SBR))
*3: Carbon black 1 (Asahi #95 manufactured by Asahi Carbon Co., Ltd., nitrogen adsorption specific surface area (N ₂ SA) = 147 m ² /g, N ₂ SA/IA = 0.98))
*4: Carbon black 2 (SEAST 7HM manufactured by Tokai Carbon Co., Ltd. (nitrogen adsorption specific surface area (N ₂ SA) = 126 m ² /g, N ₂ SA/IA = 1.05))
*5: Carbon black 3 (CD2019 manufactured by Columbian Carbon (nitrogen adsorption specific surface area (N ₂ SA) = 340 m ² /g, N ₂ SA/IA = 1.05))
*6: Carbon black 4 (Toka Black #5500 manufactured by Tokai Carbon Co., Ltd. (nitrogen adsorption specific surface area (N ₂ SA) = 225 m ² /g, N ₂ SA/IA = 0.88))
* 7: Tackifier resin (Neopolymer 140 manufactured by ENEOS Co., Ltd., C9 petroleum resin)
*8: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu K.K.)
* 9: Styrenated phenol compound 1 (SP-F manufactured by Sanko Co., Ltd. Monostyrenated phenol 65 mol% or more, distyrenated phenol 32 mol% or less, tristyrenated phenol 1 mol% or less)
* 10: Styrenated phenol compound 2 (SP-24 manufactured by Sanko Co., Ltd. Monostyrenated phenol 0 mol%, distyrenated phenol 60 mol% or more, tristyrenated phenol 40 mol% or less)
* 11: Styrenated phenol compound 3 (TSP manufactured by Sanko Co., Ltd. Monostyrenated phenol 0 mol%, distyrenated phenol 30 mol% or less, tristyrenated phenol 65 mol% or more)
* 12: Stearic acid (bead stearic acid YR manufactured by NOF Corporation)
*13: Zinc oxide (Type 3 zinc oxide manufactured by Seido Chemical Industry Co., Ltd.)
* 14: Anti-aging agent (6PPD manufactured by Flexis)
*15: Vulcanization accelerator (Noccellar CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
*16: Sulfur (fine sulfur powder containing Kinkain oil manufactured by Tsurumi Chemical Industry Co., Ltd.)

From the results in Table 1, the rubber compositions of Examples 1 and 2 are 50 to 200 parts by mass of specific carbon black with respect to 100 parts by mass of diene rubber containing SBR having a styrene content of 30% by mass or more. 5 to 50 parts by mass of a styrenated phenol compound represented by formula (1) and 20 parts by mass or more of a tackifying resin are blended, and the amount of the styrenated phenol compound is the same as the tackifying resin. Since it is 15% by mass or more, it can be seen that the dry grip performance and the graining performance are enhanced, and the temperature dependency of hardness is suppressed to improve the heat sag performance as compared with the rubber composition of the standard example.
On the other hand, in Comparative Example 1, since n in the structural formula (1) includes 1, the dry grip performance was lowered.
In Comparative Examples 2 and 3, since the N ₂ SA/IA of carbon black exceeded the upper limit specified in the present invention, the dry grip performance or breaking strength decreased.
In Comparative Example 4, since the N ₂ SA/IA of carbon black was less than the lower limit specified in the present invention, the breaking strength was lowered.
In Comparative Example 5, the blending amount of the styrenated phenol compound was less than 15% by mass with respect to the tackifying resin, so the temperature dependence and embrittlement temperature were deteriorated.
In Comparative Example 6, the styrene content of SBR was less than the lower limit specified in the present invention, so the dry grip performance and breaking strength were deteriorated.

Claims (4)

For 100 parts by mass of a diene rubber containing a styrene-butadiene copolymer rubber having a styrene content of 30% by mass or more,
The nitrogen adsorption specific surface area N ₂ SA is 100 to 500 m ² /g, and N ₂ SA is the ratio of the nitrogen adsorption specific surface area N ₂ SA (unit: m ² /g) to the iodine adsorption amount IA (unit: mg/g). 50 to 200 parts by mass of carbon black with /IA of 0.90 to 1.03,
10 to 40 parts by mass of a styrenated phenol compound represented by the following structural formula (1);
A rubber composition for tires comprising 30 to 80 parts by mass of a tackifying resin, and wherein the amount of the styrenated phenol compound is 20 to 80% by mass with respect to the tackifying resin.

(In Structural Formula (1), n is 2 or 3, and the proportion of the monostyrenated phenol compound is 0.1% by mass or less with respect to the entire styrenated phenol compound used) The rubber composition for tires according to claim 1, wherein the tackifying resin has a softening point of 60 to 180°C. The tackifier resin is at least one selected from C9 petroleum resins, phenolic resins, coumarone-indene resins, terpene resins, styrene resins, acrylic resins, rosin resins and dicyclopentadiene resins. The rubber composition for tires according to claim 1 or 2. A tire using the tire rubber composition according to any one of claims 1 to 3 for a cap tread.