JP7323813B2 - Tire rubber composition and tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber composition for tires and a tire using the same, and more specifically, it has excellent steering stability and improves wet grip performance, especially warm-up performance (wet grip performance at low temperatures), TECHNICAL FIELD The present invention relates to a rubber composition for tires that increases breaking strength and is also excellent in wear resistance, and a tire using the same.

In general, pneumatic tires for racing are available in dry road running tires and wet road running tires, and the optimum tire is selected according to the weather and road conditions during running. Here, as a competition tire for driving on wet roads, in order to improve wet grip performance, means such as (1) compounding silica having a high specific surface area, (2) compounding a large amount of silica, and (3) compounding a large amount of resin. is taken. However, in the means (1) and (2), wear resistance deteriorates due to deterioration of silica dispersibility, and in the means (3), warm-up performance (wet grip performance at low temperatures) deteriorates. there is a point

As an attempt to improve wet grip performance, for example, Patent Document 1 below discloses a rubber composition in which silica having a high specific surface area and resin components having a high Tg and a low Tg are blended with a diene rubber.
However, with this technology, it is difficult to improve both wet grip performance and wear resistance.

JP 2007-186567 A

An object of the present invention is to provide a rubber composition for tires that has excellent steering stability, improves wet grip performance, especially warm-up performance (wet grip performance at low temperatures), increases breaking strength and has excellent wear resistance, and It is to provide a tire using it.

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

That is, in the present invention, 150 parts of silica having a nitrogen adsorption specific surface area N ₂ SA of 100 to 300 m ² /g is added 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. ~300 parts by mass, 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 present invention provides a rubber composition for tires, characterized in that the content of the tackifying resin is 15% by mass or more.

(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 silica having specific properties with a diene rubber having a specific composition, and further blending a specific amount of a styrenated phenol compound. A rubber composition for tires that has excellent steering stability, improves wet grip performance, especially warm-up performance (wet grip performance at low temperatures), increases breaking strength and has excellent wear resistance, and a tire using the same. can provide.

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 wet grip performance, steering stability, and wear resistance of the tire can be enhanced. A more preferable styrene content is 33 to 50% by mass.

(silica)
The silica used in the present invention has a nitrogen adsorption specific surface area N ₂ SA of 100 to 300 m ² /g (hereinafter sometimes referred to as specific silica).
If the N ₂ SA of silica is less than 100 m ² /g, the hardness and breaking strength are lowered, resulting in poor handling stability and wear resistance.
If the N ₂ SA of silica exceeds 300 m ² /g, the viscosity becomes too high and processing becomes difficult.
A more preferred N ₂ SA of the silica used in the present invention is 130-270 m ² /g.
Note that N ₂ SA shall be measured according to JIS K6217-2.

(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 the diene rubber and silica to improve steering stability, wet grip performance, warm-up performance and wear resistance.

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 150 to 300 parts by mass of specific silica, 5 to 50 parts by mass of a styrenated phenol compound represented by the structural formula (1), and a tackifying resin, based on 100 parts by mass of diene rubber. 20 parts by mass or more, and the blending amount of the styrenated phenol compound is 15% by mass or more with respect to the tackifying resin.
When the content of the specific silica is less than 150 parts by mass, the hardness is lowered and the steering stability is deteriorated.
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 wet grip performance is lowered.
If the content of the styrenated phenol compound is less than 15% by mass relative to the tackifying resin, the hardness at low temperature is lowered, resulting in poor warm-up performance.

In the rubber composition of the present invention, the amount of the specific silica compounded is preferably 160 to 280 parts by mass, more preferably 170 to 260 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 amount of the tackifying resin compounded is preferably 25 to 70 parts by mass, more preferably 30 to 60 parts by mass, per 100 parts by mass of the diene rubber.
The content of the styrenated phenol compound is preferably 20 to 70% by mass with respect to the tackifying resin.

The rubber composition of the present invention further contains 2 to 20% by mass, preferably 5 to 16% by mass of a silane coupling agent with respect to the silica, and the silane coupling agent has the following composition (2): If it is represented by the formula, wet grip performance can be further improved.
(A) _a (B) _b (C) _c (D) _d (R1) _e SiO _{(4-2a-bcde)/2} (2)
(In formula (2), A is a divalent organic group containing a sulfide group, B is a monovalent hydrocarbon group having 5 to 10 carbon atoms, C is a hydrolyzable group, and D is an organic group containing a mercapto group. group, R1 represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, 0≦a<1, 0<b<1, 0<c<3, 0≦d<1, 0≦e<2, and It satisfies the relationship 0<2a+b+c+d+e<4.)

A silane coupling agent (polysiloxane) represented by Formula (2) and a method for producing the same are disclosed, for example, in International Publication WO2014/002750 and are publicly known.

In formula (2) above, A represents a divalent organic group containing a sulfide group. Among them, a group represented by the following formula (12) is preferable.
^* -( _CH2 ) _n - _Sx- ( _CH2 ) _n- ^* (12)
In the above formula (12), n represents an integer of 1-10, preferably an integer of 2-4.
In the above formula (12), x represents an integer of 1-6, preferably an integer of 2-4.
In the above formula (12), * indicates a bonding position.
Specific examples of the group represented by formula (12) include ^* -CH ₂ -S ₂ -CH ₂ - ^* , ^* -C ₂ H ₄ -S ₂ -C ₂ H ₄ - ^* , ^* - _C3H6 - _{S2 - C3H6-} ^* , ^* _-C4H8 - _S2 - _C4H8- ^* _, ^* _{-CH2- S4 - CH2- *} ^{, *} _{-C2H 4} - _{S4 - C2H4-} ^* , ^* _{-C3H6 - S4 - C3H6-} ^* , ^* _{-C4H8 - S4 - C4H8-} ^* and the like.

In the above formula (2), B represents a monovalent hydrocarbon group having 5 to 20 carbon atoms, and specific examples thereof include hexyl group, octyl group and decyl group. B is preferably a monovalent hydrocarbon group having 5 to 10 carbon atoms.

In formula (2) above, C represents a hydrolyzable group, and specific examples thereof include an alkoxy group, a phenoxy group, a carboxyl group, an alkenyloxy group, and the like. Among them, a group represented by the following formula (13) is preferable.
^* -OR ² (13)
In the above formula (13), R ² is an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 6 to 10 carbon atoms (arylalkyl group) or an alkenyl group having 2 to 10 carbon atoms. Among them, an alkyl group having 1 to 5 carbon atoms is preferable. Specific examples of the alkyl group having 1 to 20 carbon atoms include methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, decyl group and octadecyl group. Specific examples of the aryl group having 6 to 10 carbon atoms include a phenyl group and a tolyl group. Specific examples of the aralkyl group having 6 to 10 carbon atoms include benzyl group and phenylethyl group. Specific examples of the alkenyl group having 2 to 10 carbon atoms include vinyl group, propenyl group and pentenyl group.
In the above formula (13), * indicates a bonding position.

In the above formula (2), D represents an organic group containing a mercapto group. Among them, a group represented by the following formula (14) is preferable.
^* -( _CH2 ) _m -SH (14)
In the above formula (14), m represents an integer of 1-10, preferably an integer of 1-5.
In the above formula (14), * indicates a bonding position.
Specific examples of the group represented by formula (14) include ^* -CH ₂ SH, ^* -C ₂ H ₄ SH, ^* -C ₃ H ₆ SH, ^* -C ₄ H ₈ SH, and ^* -C _{5 . H10SH ,} ^* _{-C6H12SH ,} ^* _-C7H14SH ^{, *} _{-C8H16SH ,} ^* _-C9H18SH , and _{* -C10H20SH .}

In formula (2) above, R1 represents a monovalent hydrocarbon group having 1 to 4 carbon atoms.

In the above formula (2), the relationships of 0≦a<1, 0<b<1, 0<c<3, 0≦d<1, 0≦e<2, and 0<2a+b+c+d+e<4 are satisfied.

In the above formula (2), a preferably satisfies 0<a≦0.50 for the reason that the effects of the present invention are improved.
In the above formula (2), b preferably satisfies 0<b, and more preferably satisfies 0.10≦b≦0.89 for the reason that the effect of the present invention is improved.
In the above formula (2), c preferably satisfies 1.2≦c≦2.0 for the reason that the effect of the present invention is improved.
In the above formula (2), d preferably satisfies 0.1≤d≤0.8 for the reason that the effect of the present invention is improved.

The weight average molecular weight of the polysiloxane is preferably 500 to 2,300, more preferably 600 to 1,500, for the reason that the effect of the present invention is improved. The molecular weight of the above polysiloxane in the present invention is determined in terms of polystyrene by gel permeation chromatography (GPC) using toluene as a solvent.
The mercapto equivalent of the polysiloxane obtained by the acetic acid/potassium iodide/potassium iodate addition-sodium thiosulfate solution titration method is preferably 550 to 700 g/mol, more preferably 600 to 650 g, from the viewpoint of excellent vulcanization reactivity. /mol is more preferred.

The above polysiloxane preferably has 2 to 50 siloxane units (--Si--O--) for the reason that the effects of the present invention are improved.

Metals other than silicon atoms (for example, Sn, Ti, Al) are not present in the skeleton of the polysiloxane.

Methods for producing the polysiloxane are known, and can be produced, for example, according to the method disclosed in International Publication WO2014/002750.

(Other ingredients)
In addition to the above components, the rubber composition of the present invention includes a vulcanizing or cross-linking agent; a vulcanizing or cross-linking accelerator; various fillers such as carbon black, clay, talc, calcium carbonate, aluminum hydroxide; Various additives generally blended in rubber compositions such as inhibitors; plasticizers; resins; curing agents can be blended. Can be used to vulcanize or crosslink. 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. In particular, the wet grip performance can be enhanced by using aluminum hydroxide. When aluminum hydroxide is blended, its blending amount is preferably 20 to 80 parts by mass with respect to 100 parts by mass of the diene rubber.

The rubber composition of the present invention is excellent in steering stability, improves wet grip performance, especially warm-up performance, increases breaking strength and has excellent wear resistance, so it is preferable for tire treads, particularly cap treads. can be suitably used for treads of competition tires, especially 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 1-4 and Comparative Examples 1-4
Preparation of sample 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 (0 ° C.): According to JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho), tan δ (0 °C) was measured. The results were indexed with the value of the standard example set to 100. A larger index indicates better wet grip performance.
Steering stability: Hardness was measured at a temperature of 60°C with a durometer type A according to JIS K6253. The results were indexed with the value of the standard example set to 100. A larger index indicates higher hardness and superior steering stability.
Warm-up performance: Hardness was measured at a temperature of 10°C with a durometer type A according to JIS K6253. The results were indexed with the value of the standard example set to 100. The smaller the index, the lower the hardness at low temperatures and the better the warm-up performance (low-temperature grip performance).
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 and the better the wear 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: Silica 1 (Evonik Ultrasil 7000GR, nitrogen adsorption specific surface area (N ₂ SA) = 175 m ² /g)
*4: Silica 2 (Zeosil 1085GR manufactured by Solvay (nitrogen adsorption specific surface area (N ₂ SA) = 80 m ² /g)
*5: Carbon black (SEAST 7HM manufactured by Tokai Carbon Co., Ltd.)
* 6: Tackifier resin (Neopolymer 140 manufactured by ENEOS Co., Ltd., C9 petroleum resin)
*7: Silane coupling agent 1 (Si69 manufactured by Evonik)
*8: Silane coupling agent 2 (a silane coupling agent prepared by the method disclosed in the pamphlet of International Publication WO2014/002750 and satisfying the composition formula (2) above. Composition formula = (-C ₃ H ₆ - S ₄ -C ₃ H ₆ -) _0.083 (-C ₈ H ₁₇ ) _0.667 (-OC ₂ H ₅ ) _1.50 (-C ₃ H ₆ SH) _0.167 SiO _0.75 , average molecular weight = 860)
* 9: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu K.K.)
* 10: 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)
*11: 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)
* 12: 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)
* 13: Stearic acid (bead stearic acid YR manufactured by NOF Corporation)
*14: Zinc oxide (Type 3 zinc oxide manufactured by Seido Chemical Industry Co., Ltd.)
* 15: Anti-aging agent (6PPD manufactured by Flexis)
* 16: Vulcanization accelerator 1 (Suncellar D-G manufactured by Sanshin Chemical Industry Co., Ltd.)
* 17: Vulcanization accelerator 2 (Noccellar CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
*18: Sulfur (fine sulfur powder containing Kinkain oil manufactured by Tsurumi Chemical Industry Co., Ltd.)
* 19: Aluminum hydroxide (trade name BF013 manufactured by Nippon Light Metal Co., Ltd.)

From the results in Table 1, the rubber compositions of Examples 1 to 4 are 150 to 300 parts by mass of specific silica with respect to 100 parts by mass of diene rubber containing SBR having a styrene content of 30% by mass or more, and the structural formula 5 to 50 parts by mass of the styrenated phenol compound represented by (1) and 20 parts by mass or more of the tackifying resin are blended, and the amount of the styrenated phenol compound is 15 parts with respect to the tackifying resin. Since it is more than mass %, it has excellent steering stability, wet grip performance, especially warm-up performance (wet grip performance at low temperature), and increased breaking strength and wear resistance compared to the standard rubber composition. It is also found to be superior in terms of sex.
On the other hand, in Comparative Example 1, since n in the structural formula (1) includes 1, the wet grip performance, steering stability, and wear resistance decreased.
In Comparative Example 2, since the N ₂ SA of silica is less than the lower limit specified in the present invention, steering stability and wear resistance are lowered.
In Comparative Example 3, the amount of silica compounded was less than the lower limit specified in the present invention, so the handling stability was lowered .
In Comparative Example 4 , the styrene content of the SBR was less than the lower limit specified in the present invention, so wet grip performance, steering stability, and wear resistance deteriorated.

Claims (5)

For 100 parts by mass of a diene rubber containing a styrene-butadiene copolymer rubber having a styrene content of 39 to 50 mass%,
150 to 300 parts by mass of silica having a nitrogen adsorption specific surface area N ₂ SA of 100 to 300 m ² /g,
10 to 40 parts by mass of a styrenated phenol compound represented by the following structural formula (1);
A rubber composition for tires, comprising 25 to 70 parts by mass of a tackifying resin, and wherein the amount of the styrenated phenol compound is 20 % by mass or more relative 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 tackifying 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. 2 to 20% by mass of a silane coupling agent having a mercapto group is further blended with the silica,
The rubber composition for tires according to any one of claims 1 to 3, wherein the silane coupling agent having a mercapto group is represented by the following compositional formula (2).
(A) _a (B) _b (C) _c (D) _d (R1) _e SiO _{(4-2a-bcde)/2} (2)
(In formula (2), A is a divalent organic group containing a sulfide group, B is a monovalent hydrocarbon group having 5 to 10 carbon atoms, C is a hydrolyzable group, and D is an organic group containing a mercapto group. group, R1 represents a monovalent hydrocarbon group having 1 to 4 carbon atoms, 0≦a<1, 0<b<1, 0<c<3, 0≦d<1, 0≦e<2, and It satisfies the relationship 0<2a+b+c+d+e<4.) A tire using the tire rubber composition according to any one of claims 1 to 4 for a cap tread.