JP2023047431A - Rubber composition for tires, and tire - Google Patents

Abstract

To improve wet grip performance, processability, and steering stability of a racing pneumatic tire.SOLUTION: A rubber composition for tires is obtained by blending 100 pts.mass of a diene rubber containing a styrene-butadiene copolymer rubber having a styrene content of 30 mass% or more with: 140-300 pts.mass of silica having a nitrogen adsorption specific surface area N2SA of 100-300 m2/g; and 15 pts.mass or more of surface-treated aluminum hydroxide.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a rubber composition for a tire and a tire using the same, and more particularly, a rubber composition for a tire having excellent wet grip performance and processability and excellent steering stability and a tire using the same. It is about.

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, competition tires for driving on wet roads are compounded with a large amount of silica or aluminum hydroxide in order to improve wet grip performance (see, for example, Patent Document 1). However, such a means increases the viscosity of the compound, and lowers the strength of the green, resulting in deterioration of workability such as adhesion to the inside of the mixer. On the other hand, if a large amount of oil is blended in order to lower the viscosity, there is a problem that the steering stability is lowered.

Japanese Patent No. 5827541

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rubber composition for tires which is excellent in wet grip performance and workability, and which is also excellent in steering stability, and a tire using the same.

As a result of extensive research, the present inventors have found that a diene rubber having a specific composition is blended with a specific amount of silica having specific characteristics, and further with a specific amount of surface-treated aluminum hydroxide. As a result, the inventors have found that the above problems can be solved, and have completed the present invention.

That is, in the present invention, 140 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 and 15 parts by mass or more of surface-treated aluminum hydroxide are blended to provide a rubber composition for tires.

The rubber composition for tires of the present invention has a nitrogen adsorption specific surface area N ₂ SA of 100 to 300 m ^{2 /} per 100 parts by mass of a diene rubber containing a styrene-butadiene copolymer rubber having a styrene content of 30% by mass or more. 140 to 300 parts by mass of silica of g and 15 parts by mass or more of surface-treated aluminum hydroxide are blended, so wet grip performance and workability are excellent, and handling stability is also improved. An excellent rubber composition for tires and a tire using the same can be provided.

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 and steering stability 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.

(surface-treated aluminum hydroxide)
The aluminum hydroxide used in the present invention is surface-treated with a surface treatment agent. Examples of such surface treatment agents include silane coupling agents, higher fatty acids or salts thereof, polymers, titanate compounds, epoxy compounds, isocyanate compounds, phosphate esters and the like. Two or more surface treatment agents may be used in combination. Among them, a silane coupling agent is preferable from the viewpoint of improving the effects of the present invention.

Silane coupling agents include vinyl group-containing silane coupling agents, (meth)acryloyl group-containing silane coupling agents, amino group-containing silane coupling agents, epoxy group-containing silane coupling agents, and mercapto group-containing silanes. coupling agents, silane coupling agents containing carboxyl groups, silane coupling agents containing halogen atoms, and the like.

The amount of the surface treatment agent used is, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of aluminum hydroxide.

As a surface treatment method for aluminum hydroxide, for example, a known method such as a dry method, a wet method, or an integral blend method may be appropriately selected.

From the viewpoint of improving the effect of the present invention, the BET specific surface area of aluminum hydroxide is preferably 10 m ² /g or less, more preferably 1 to 8 m ² /g. The BET specific surface area is measured according to ISO5794/1.

As the surface-treated aluminum hydroxide, commercially available products such as the Martinal series manufactured by Huber can be used.

(Mixing ratio of rubber composition)
The rubber composition of the present invention is characterized by blending 140 to 300 parts by mass of specific silica and 15 parts by mass or more of surface-treated aluminum hydroxide with respect to 100 parts by mass of diene rubber.
When the content of the specific silica is less than 140 parts by mass, the hardness is lowered and the steering stability is deteriorated.
If the content of the surface-treated aluminum hydroxide is less than 15 parts by mass, the wet grip performance cannot be improved.

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 surface-treated aluminum hydroxide compounded is preferably 10 to 80 parts by mass, more preferably 20 to 70 parts by mass, per 100 parts by mass of the diene rubber.

(Liquid styrene-butadiene copolymer)
The rubber composition of the present invention can be blended with a liquid styrene-butadiene copolymer (liquid SBR) in order to further improve its effects.
The liquid SBR preferably has a vinyl content of 50% by mass or more (preferably 50 to 90% by mass) and is unmodified. The liquid SBR has a weight average molecular weight of 2,000 to 40,000, preferably 3,000 to 20,000. In addition, the weight average molecular weight said by this invention means the weight average molecular weight of polystyrene conversion analyzed by a gel permeation chromatography (GPC). The liquid SBR used in the present invention is liquid at 23°C. Therefore, it is distinguished from the diene rubber, which is solid at this temperature.
The amount of the liquid SBR compounded is preferably 5 parts by mass or more, more preferably 5 to 50 parts by mass, per 100 parts by mass of the diene rubber.

(tackifying resin)
The rubber composition of the present invention can be blended with a tackifying resin in order to further improve its effect.
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.

The amount of the tackifying resin is preferably 15 parts by mass or more, more preferably 25 to 70 parts by mass, particularly 30 to 60 parts by mass, based on 100 parts by mass of the diene rubber. preferable.

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 represented by the formula, wet grip performance, workability and steering stability 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 effect of the present invention is 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; carbon black, clay, talc, various fillers such as calcium carbonate; Various additives that are generally blended in rubber compositions such as agents; resins; 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.

Since the rubber composition of the present invention is excellent in wet grip performance and workability, and is also excellent in steering stability, it is suitably used for tire treads, particularly cap treads, preferably racing tire treads, particularly cap treads. can be 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.

Manufacturing method of modified liquid SBR By using lithium dimethylamide as an initiator, the polymerization active terminal of solution-polymerized styrene-butadiene rubber synthesized by anionic polymerization from styrene and 1,3-butadiene is reacted with methyltriethoxysilane as a modifier. , to obtain a modified liquid SBR with terminal modification.

Standard Example, Examples 1-8 and Comparative Examples 1-5
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, a pneumatic tire having a tire size of 225/40R18 was produced by using the rubber composition in the tread portion and vulcanizing it, and the following evaluations were performed.

Wet grip performance: The obtained pneumatic tire was mounted on a wheel with a rim size of 17 x 8J, mounted on a domestic 2-liter class test vehicle, and the actual vehicle was driven under the air pressure of 240 kPa. The water depth below the top of the unevenness) was measured on a test course of 1.2 km per lap, and the lap time was measured for each lap when running 10 laps continuously, and the fastest lap time was taken as the result. The results were indexed with the value of Standard Example 1 set to 100. A larger index indicates a faster lap time and better wet grip performance.

Processability 1 (Mooney viscosity): Using the above rubber composition (unvulcanized), the Mooney viscosity of the unvulcanized rubber at 100°C was measured according to JIS K6300. The results were indexed with the value of the standard example set to 100. A larger index indicates lower viscosity and better processability.

Processability 2 (green strength): Using the above rubber composition (unvulcanized), in accordance with JIS K6251: 2010, a JIS No. 3 dumbbell-shaped test piece (thickness 2 mm) was punched out at a temperature of 20 ° C. and a tensile speed of 500 mm / The 300% modulus was measured under conditions of minutes. The results were indexed with the value of the standard example set to 100. A larger index indicates better green strength and better workability.

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.

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 (VN3GR manufactured by Evonik, nitrogen adsorption specific surface area (N ₂ SA) = 181 m ² /g)
*4: Silica 2 (Zeosil 1085GR manufactured by Solvay (nitrogen adsorption specific surface area (N ₂ SA) = 86 m ² /g, N ₂ SA/CTAB = 0.99)
*5: Carbon black (SEAST 9 manufactured by Tokai Carbon Co., Ltd. (nitrogen adsorption specific surface area (N ₂ SA) = 142 m ² /g, N ₂ SA/IA = 1.02))
*6: Aluminum hydroxide 1 (Martinal OL-104LEO manufactured by Huber (no surface treatment))
*7: Aluminum hydroxide 2 (Martinal OL-104C manufactured by Huber (surface treated with stearic acid))
*8: Aluminum hydroxide 3 (Martinal OL-104GO manufactured by Huber (surface treated with polymer))
*9: Aluminum hydroxide 4 (Martinal OL-104IO manufactured by Huber (surface treated with aminosilane))
*10: Aluminum hydroxide 5 (Martinal OL-104ZO manufactured by Huber (surface treated with vinylsilane))
*11: Tackifier resin 1 (Neopolymer 140S manufactured by ENEOS Co., Ltd., C9 petroleum resin, softening point = 145 ° C.)
*12: Tackifier resin 2 (YS resin TO-125 manufactured by Yasuhara Chemical Co., Ltd., softening point = 125 ° C.)
*13: Silane coupling agent 1 (Si69 manufactured by Evonik)
*14: Silane coupling agent 2 (a silane coupling agent prepared by the method disclosed in 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)
*15: Liquid SBR1 (Cray Valley Ricon100, vinyl content = 70% by mass, unmodified)
*16: Liquid SBR2 (Ricon184 manufactured by Cray Valley, vinyl content = 30% by mass, unmodified)
*17: Liquid SBR3 (modified liquid SBR based on the above manufacturing method, vinyl content = 70% by mass, silane-modified)
* 18: Plasticizer (Extract No. 4S manufactured by Shell Lubricants Japan Co., Ltd.)
* 19: Stearic acid (bead stearic acid YR manufactured by NOF Corporation)
*20: Zinc oxide (Type 3 zinc oxide manufactured by Seido Chemical Industry Co., Ltd.)
* 21: Anti-aging agent (6PPD manufactured by Flexis)
* 22: Vulcanization accelerator 1 (Suncellar D-G manufactured by Sanshin Chemical Industry Co., Ltd.)
* 23: Vulcanization accelerator 2 (Noccellar CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
*24: Sulfur (fine sulfur powder containing Kinkain oil manufactured by Tsurumi Chemical Industry Co., Ltd.)

From the results in Table 1, the rubber composition of each example has a nitrogen adsorption specific surface area N ₂ SA 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. It is characterized by blending 140 to 300 parts by mass of 100 to 300 m ² /g of silica and 15 parts by mass or more of surface-treated aluminum hydroxide. Excellent stability.
On the other hand, in Comparative Examples 1 and 2, the aluminum hydroxide was not surface-treated, so workability deteriorated.
In Comparative Example 3, since the N ₂ SA of silica was less than the lower limit specified in the present invention, workability and steering stability were lowered.
In Comparative Example 4, the styrene content of the SBR was less than the lower limit specified in the present invention, and the aluminum hydroxide was not surface-treated, so workability and handling stability were lowered.
In Comparative Example 5, the styrene content of SBR was less than the lower limit specified in the present invention, so the workability was lowered.

Claims (6)

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,
140 to 300 parts by mass of silica having a nitrogen adsorption specific surface area N ₂ SA of 100 to 300 m ² /g, and 15 parts by mass or more of surface-treated aluminum hydroxide,
A rubber composition for tires characterized by being compounded. 2. The rubber composition for a tire according to claim 1, wherein said surface-treated aluminum hydroxide is aluminum hydroxide surface-treated with a silane coupling agent. 3. The rubber composition for tires according to claim 1, further comprising 5 parts by mass or more of an unmodified liquid styrene-butadiene copolymer rubber having a vinyl content of 50% by mass or more. thing. The rubber composition for tires according to any one of claims 1 to 3, further comprising 15 parts by mass or more of a tackifying resin having a softening point of 60 to 180°C. 2 to 20% by mass of a silane coupling agent is further blended with the silica,
The rubber composition for tires according to any one of claims 1 to 4, 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 5 for a cap tread.