JP5386886B2 - Rubber composition for tire side tread and pneumatic tire using the same - Google Patents

Description

  The present invention relates to a rubber composition for a tire side tread and a pneumatic tire using the same, and more particularly to a rubber composition for a tire side tread which is highly elastic and excellent in low heat generation and a pneumatic tire using the same.

  With the demand for lower fuel consumption of automobiles, tire rubber compositions are required to have low heat buildup. In order to reduce the exothermic property, generally, there are methods of increasing the particle size of carbon black used as a filler and reducing the amount of the compound. However, in the case of a rubber composition for a side tread of a tire, there is a problem that when the amount of carbon black is reduced, the elastic modulus is greatly reduced. In addition, there is a method of blending silica in place of carbon black in order to reduce heat generation, but there is also a problem that workability is deteriorated.

Patent Document 1 listed below discloses a polymer or copolymer obtained by solution polymerization of a conjugated diene monomer or a conjugated diene monomer and an aromatic vinyl monomer using an organic active metal catalyst. There is disclosed a modified conjugated diene polymer rubber obtained by reacting a siloxane compound having at least one ketimine group and at least two alkoxysilyl groups in the molecule at the polymerization active terminal. However, Patent Document 1 includes mixing a carbon black having a specific nitrogen adsorption specific surface area (N ₂ SA), and a sulfur / vulcanization accelerator blending ratio which is a preferred embodiment of the present invention described below. There is no disclosure or suggestion of proper control.
International Publication WO2007 / 018018 Pamphlet

  An object of the present invention is to provide a rubber composition for a tire side tread having high elasticity and excellent low heat buildup without impairing processability, and a pneumatic tire using the same.

The present invention is as follows.
1. 5 to 60 carbon blacks having a nitrogen adsorption specific surface area (N ₂ SA) of 20 to 50 m ² / g with respect to 100 parts by mass of diene rubber composed of 30 parts by mass or more of natural rubber and 5 to 70 parts by mass of the modified butadiene rubber described below. A tire side tread characterized by containing a mass part, further containing sulfur and a vulcanization accelerator, and having a sulfur / vulcanization accelerator blending ratio (mass ratio) of 1.75 to 1.9. Rubber composition.
Modified butadiene rubber: A modified butadiene obtained by reacting a compound represented by the following formula (I) or (II) with a polymerization active terminal of a polymer obtained by solution polymerization of a butadiene monomer using an organic active metal catalyst. Rubber.

[Chemical 1]

(In formula (I), A _{1 to} A ₃ are each independently any one of an alkoxyl group, an alkyl group, an aryl group, and hydrogen, and R ₁ includes N, O, S, and P. A linear, alicyclic or aromatic hydrocarbon group having 1 to 30 carbon atoms, and A ₄ and A ₅ each independently represents an organic group which may contain Si, O, N, and S. R ₂ and R ₃ are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms, and R ₂ and R ₃ are simultaneously hydrogenated. And m is an integer from 0 to 20 and n is an integer from 2 to 20)

[Chemical 2]

(In the formula (II), _{R 1} is N, O, a hydrocarbon group having 1 to 30 carbon atoms, including S, straight may also include P, and alicyclic or _aromatic, R 2 to R ₆ Are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 18 carbon atoms, and any one of R ₂ and R ₃ can represent hydrogen, and n is an integer of 2 to 20 Is)
2. The rubber composition for a tire side tread further includes sulfur and a vulcanization accelerator, and a mixing ratio (mass ratio) of the sulfur / vulcanization accelerator is 1.7 to 2.0. 2. The rubber composition for a tire side tread as described in 1 above.
3. 3. The tire side tread rubber composition according to 1 or 2, wherein the tire side tread rubber composition has a Shore A hardness of 50 to 60 at 20 ° C.
4). The pneumatic tire which used the rubber composition in any one of said 1-3 for the side tread.

According to the present invention, a specific amount of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 50 m ² / g or less is blended with a diene rubber blended with a specific modified butadiene rubber. A rubber composition for a tire side tread that is highly elastic and excellent in low heat build-up and a pneumatic tire using the same can be provided without loss.

Hereinafter, the present invention will be described in more detail.
The modified butadiene rubber used in the present invention is a compound represented by the following formula (I) or (II) at the polymerization active terminal of a polymer obtained by solution polymerization of a butadiene monomer using an organic active metal catalyst. It is made to react.

[Chemical 3]

(In formula (I), A _{1 to} A ₃ are each independently any one of an alkoxyl group, an alkyl group, an aryl group, and hydrogen, and R ₁ includes N, O, S, and P. A linear, alicyclic or aromatic hydrocarbon group having 1 to 30 carbon atoms, and A ₄ and A ₅ each independently represents an organic group which may contain Si, O, N, and S. R ₂ and R ₃ are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms, and R ₂ and R ₃ are simultaneously hydrogenated. And m is an integer from 0 to 20 and n is an integer from 2 to 20)

[Chemical 4]

(In the formula (II), _{R 1} is N, O, a hydrocarbon group having 1 to 30 carbon atoms, including S, straight may also include P, and alicyclic or _aromatic, R 2 to R ₆ Are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 18 carbon atoms, and any one of R ₂ and R ₃ can represent hydrogen, and n is an integer of 2 to 20 Is)

  As the organic active metal catalyst used in the present invention, an organic alkali metal compound is preferably used. For example, organic monometallic compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium and stilbenelithium are used. Lithium compounds; organic polyvalent lithium compounds such as dilithiomethane, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene; organic sodium compounds such as sodium naphthalene; potassium naphthalene, etc. Of the organic potassium compound. In addition, 3,3- (N, N-dimethylamino) -1-propyllithium, 3- (N, N-diethylamino) -1-propyllithium, 3- (N, N-dipropylamino) -1- Propyllithium, 3-morpholino-1-propyllithium, 3-imidazole-1-propyllithium, and organolithium compounds in which these are chain-extended with 1 to 10 units of butadiene, isoprene, or styrene can also be used.

In the compound represented by the formula (I), A _{1 to} A ₃ are each independently, for example, an alkoxyl group having 1 to 18 carbon atoms, such as an alkyl group having 1 to 18 carbon atoms, such as an aryl having 6 to 18 carbon atoms. R ₁ is any one of a group and hydrogen, and R ₁ is a linear, alicyclic or aromatic hydrocarbon group that may contain N, O, S, P, specifically, Is a methylene group, ethylene group, propylene group, phenylene group, toluylene group, or an atomic group (group) formed by bonding these via an imino bond, an ether bond, a thioether bond, or a phosphine, and A ₄ and A ₅ are each independently, Si, O, N, organic group which may contain S, represents hydrogen or a hydroxyl group, specifically a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a phenoxy group, main Group, an ethyl group, butyl group, propyl group, phenyl group, hydrogen, hydroxyl, trimethylsilyl group, a triethylsilyl group, _{R 2} and _{R 3} are each independently 1 to 20 carbon atoms, preferably 1 to 15 Alkyl group, specifically methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, isopentyl group or aryl group having 6 to 18 carbon atoms, preferably 6 to 12 carbon atoms, specifically Is a phenyl group, a toluyl group, or a naphthyl group, but R ₂ and R ₃ are not hydrogen at the same time, m is an integer of 0 to 20, preferably 5 to 15, n is cold flow property, workability, etc. In view of the above, it is an integer of 2 to 20, preferably an integer of 5 to 15. )

In the compound represented by the above (II), R ₁ is a carbon atom having 1 to 30 carbon atoms, preferably 1 to 18 carbon atoms, which may contain N, O, S, and P, a straight chain, an alicyclic ring or an aromatic ring. A hydrogen group, specifically a methylene group, an ethylene group, a propylene group, a phenylene group, a toluylene group, or an atomic group (group) formed by bonding these via an imino bond, an ether bond, a thioether bond, or a phosphine. R _{2 to} R ₆ are each independently an alkyl group having 1 to 20 carbon atoms, specifically a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, an isopentyl group, or 6-18 carbon atoms, preferably 6 to 12 aryl group, specifically a phenyl group, toluyl group, naphthyl group and the like, either one of R ₂ and R ₃ represent hydrogen Can, and n-cold flow property, an integer from the viewpoint 2-20, such as processability, preferably 5 to 15 integer. )

  The compound represented by the formula (I) or (II) is a compound obtained by reacting a silane compound having a primary amino group with a carbonyl compound, and the silane having a primary amino group used here. Compounds include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxylane, N- (2-aminoethyl) -3-aminopropyl Examples thereof include methyldimethoxysilane and N- (2-aminoethyl) -3-aminopropyltrimethoxysilane. On the other hand, as carbonyl compounds, acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, cyclohexanone, methylcyclohexanone, methylcyclohexyl ketone, acetophenone, benzophenone and other general-purpose ketone compounds, or methanol, ethanal , General purpose aldehydes such as propanal, 2-methylpropanal, butanal, 2-methylbutanal, pentanal, 2-methylpentanal, benzaldehyde, toluylaldehyde, 2,4-dimethylbenzaldehyde, and p-isobutylbenzaldehyde are preferably used. be able to. Further, tetramethoxysilane, tetraethoxysilane, diethoxydimethylsilane, dimethoxydimethylsilane, dimethoxydiphenylsilane, dimethoxymethylphenylsilane, n-dodecyltriethoxysilane, ethyltriethoxysilane, n-hexyltrimethoxysilane, methyl Triethoxysilane, n-octadecyltriethoxysilane, octadecyltrimethoxysilane, pentyltriethoxysilane, pentyltrimethoxysilane, and the like can be added and reacted.

  Further, the modified butadiene rubber of the present invention coexists or reacts with moisture present in the atmosphere or environment to generate primary amino groups, and the modified butadiene rubber in such a state is also useful in the present invention.

  In combination with the compound represented by the formula (I) or (II) used in the present invention, tin compound, silicon compound, amide compound and / or imide compound, isocyanate and / or isothiocyanate compound, ketone compound, ester Compounds, vinyl compounds, oxirane compounds, thiirane compounds, polysulfide compounds, halogen compounds, fullerenes, and the like may be added as modifiers or coupling agents.

  The diene rubber used in the present invention is composed of natural rubber and the above-mentioned modified butadiene rubber. In 100 parts by mass of the diene rubber, 30 parts by mass or more of natural rubber and 5 to 70 parts by mass of the above-mentioned modified butadiene rubber are used. If the blending amount of the natural rubber is less than 30 parts by mass, the strength and elastic modulus are undesirably lowered. Further, if it is less than 5 parts by mass of the modified butadiene rubber, the effect of the present invention is small, and if it exceeds 70 parts by mass, the strength and elastic modulus are undesirably lowered. More preferably, the natural rubber is 30 parts by mass or more and the modified butadiene rubber is 40 to 70 parts by mass in 100 parts by mass of the diene rubber.

The rubber composition for a tire side tread of the present invention has a nitrogen adsorption specific surface area (N ₂ SA) (measured according to JIS K6217-2) of 50 m ² / g or less, preferably 20 to 50 m ² / g, more preferably. 5 to 60 parts by mass, preferably 25 to 50 parts by mass, of carbon black of 25 to 45 m ² / g with respect to 100 parts by mass of the diene rubber. If the nitrogen adsorption specific surface area (N ₂ SA) exceeds 50 m ² / g, the desired low heat build-up cannot be exhibited, which is not preferable. Further, when the blending amount of carbon black is less than 5 parts by mass, the strength is insufficient, and when it exceeds 60 parts by mass, the heat generation becomes high, which is not preferable.

  In the rubber composition for a tire side tread of the present invention, the mixing ratio (mass ratio) of sulfur and vulcanization accelerator sulfur / vulcanization accelerator is preferably 1.7 to 2.0. Within the range of this blending ratio, the effects of the present invention can be improved, and at the same time, fatigue resistance and strength can be enhanced. A more preferable blending ratio (mass ratio) is 1.75 to 1.9.

  As the vulcanization accelerator used in the present invention, any conventionally known vulcanization accelerator can be used. For example, thiuram vulcanization accelerator, sulfenamide vulcanization accelerator, guanidine vulcanization accelerator, thiazole And the like. Among them, a thiazole vulcanization accelerator is preferable.

  The tire side tread rubber composition preferably has a Shore A hardness of 50 to 60 at 20 ° C., and can be suitably used as a tire side tread.

  In addition to the components described above, the rubber composition for tire side treads of the present invention is generally blended with tire rubber compositions such as reinforcing fillers such as silica, various oils, anti-aging agents, and plasticizers. Various additives that are used can be blended, and such additives can be kneaded by a general method to form a composition. The blending amounts of these additives can be set to conventional general blending amounts as long as the object of the present invention is not violated. The rubber composition according to the present invention can be suitably used for a side tread of a pneumatic tire, and can be used as it is in a conventional general production line for pneumatic tires.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Synthesis Example of Compound Represented by Formula (II) 0.112 mol of 3-aminopropyltrimethoxysilane and 0.123 mol of methyl isopropyl ketone were stirred at room temperature for 2 days in a nitrogen atmosphere. Methanol and unreacted methyl isopropyl ketone were removed from the obtained reaction solution under vacuum to obtain a ketimine silane condensate having an average condensation degree of 2.4.

Example of synthesis of modified butadiene rubber A 10 L autoclave reactor purged with nitrogen was charged with cyclohexane, 9.215 mol of butadiene and 5.464 mmol of 1,1,4,4, -tetramethylethylenediamine (TMEDA), and stirring was started. . After the temperature of the contents in the reaction vessel was 50 ° C., 4.856 mmol of n-butyllithium was added. After the polymerization conversion reached 100%, 6.8 g of 10.3% by mass toluene solution of the ketimine silane condensate synthesized above was added and stirred for 1 hour, and further 0.5 mL of methanol was added for 30 minutes. The mixture was stirred, a small amount of an antioxidant (Irganox 1520) was added to the resulting polymer solution, and the solvent was removed by concentration under reduced pressure. The polymer was coagulated and washed in methanol, and then dried to obtain a solid polymer (modified butadiene rubber).
The obtained modified butadiene rubber had a mass average molecular weight of 350,000.

Examples 1-7 and Comparative Examples 1-7
Sample Preparation In the formulation (parts by mass) shown in Table 1, the components other than the vulcanization accelerator and sulfur were kneaded for 5 minutes with a 0.6 liter closed mixer. A vulcanization accelerator and sulfur were added to the obtained master batch and kneaded with an 8-inch open roll to obtain a rubber composition. Next, the obtained rubber composition was press vulcanized at 160 ° C. for 30 minutes in a predetermined mold to prepare a vulcanized rubber test piece. Using the obtained rubber composition and vulcanized rubber test piece, the physical properties were measured by the following test methods.

tan δ: Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho, measurement was performed under the conditions of an elongation deformation strain rate of 10 ± 2%, a frequency of 20 Hz, and a temperature of 60 ° C. Using Comparative Example 1 as a reference (100), the larger the index, the lower the tan δ and the lower the heat buildup.
Hardness: Measured according to JIS K6253.
Elastic modulus: The dynamic elastic modulus was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho under the conditions of an elongation deformation strain rate of 10 ± 2%, a frequency of 20 Hz, and a temperature of 60 ° C. Using Comparative Example 1 as a reference (100), the larger the index, the higher the elastic modulus.
Viscosity: Mooney viscosity at 100 ° C. was measured according to JIS K6300. Using Comparative Example 1 as a reference (100), the smaller the index, the lower the viscosity and the better the workability.
Fatigue resistance: Based on JIS K6270, 100% distortion was repeatedly given to No. 3 dumbbell, and evaluated by measuring the number of breaks. Using Comparative Example 1 as a reference (100), the larger the index, the better the fatigue resistance.
Strength: Measured according to JIS K6251. Using Comparative Example 1 as a reference (100), the larger the index, the higher the strength.
The results are shown in Table 1.

* 1: NR (RSS # 3)
* 2: BR (Nippon ZEON Co., Ltd., Nipol BR1220)
* 3: Modified BR (modified butadiene rubber synthesized in the above synthesis example)
* 4: Carbon black a (Nikka Chemical Co., Ltd., Niteron # 10S, nitrogen adsorption specific surface area (N ₂ SA) = 43 m ² / g, average particle diameter = 44 nm)
* 5: Carbon black b (Nisshin Carbon Co., Ltd., Niteron # 55U, nitrogen adsorption specific surface area (N ₂ SA) = 35 m ² / g, average particle size = 56 nm)
* 6: Carbon black c (Nikka Carbon Co., Ltd., Niteron # 200, nitrogen adsorption specific surface area (N ₂ SA) = 78 m ² / g, average particle size = 29 nm)
* 7: Silica (Tosoh Silica Co., Ltd., Nipsil AQ)
* 8: Silane coupling agent (De69, Si69)
* 9: Zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd., three types of zinc oxide)
* 10: Stearic acid (manufactured by NOF Corporation, bead stearic acid)
* 11: Anti-aging agent (manufactured by Flexis, SANTOFLEX 6PPD)
* 12: Wax (Sannok, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 13: Aroma oil (Extract No. 4 S, Showa Shell Sekiyu KK)
* 14: Sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd., fine powdered sulfur with Jinhua seal oil, containing 100 parts by mass of oil with respect to 100 sulfur)
* 15: Vulcanization accelerator (Ouchi Shinsei Chemical Co., Ltd., Noxeller NS-P)

Comparing Example 1 and Comparative Example 2, in Example 1, by replacing the general-purpose butadiene rubber with the modified butadiene rubber, reduction in heat generation and improvement in elastic modulus could be achieved without impairing processability. Also, fatigue resistance and strength are improved. In Example 2, since the ratio of the modified butadiene rubber was increased, the exothermic property could be further reduced. Example 3 and Comparative Example 1 are examples in which carbon black having a small particle diameter is used. When both are compared, Example 3 has all of elastic modulus, low heat build-up, workability, fatigue resistance, and strength. Excellent results. Example 4 is an example in which part of the carbon black was replaced with silica, but the results were excellent in all of the elastic modulus, low heat build-up, workability, and strength compared to Comparative Example 3 using a general-purpose butadiene rubber. It became. Example 5 is an example in which the compounding amount of sulfur is increased, and the compounding ratio (mass ratio) of sulfur / vulcanization accelerator is 1.90, which is outside the preferable range of the present invention. Compared to, fatigue resistance is slightly worse. Example 6 is an example in which the blending amount of sulfur is reduced, and the blending ratio (mass ratio) of sulfur / vulcanization accelerator is 1.42, which is outside the preferred range of the present invention. Compared with, strength is slightly worse. Example 7 is an example in which the compounding amount of sulfur is increased, and the compounding ratio (mass ratio) of sulfur / vulcanization accelerator is 2.02, which is outside the preferable range of the present invention. Compared to, fatigue resistance is slightly worse. Example 7 is a reference example.
Comparative Example 4 is an example in which a general-purpose butadiene rubber is used and the blending ratio (mass ratio) of sulfur / vulcanization accelerator is 1.42. The elastic modulus, workability, and strength are not improved, and the tire It is not suitable as a rubber composition for a side tread. Comparative Example 5 is an example in which a general-purpose butadiene rubber is used and the blending ratio (mass ratio) of sulfur / vulcanization accelerator is set to 2.02, and improvements are seen in the elastic modulus, low heat build-up, and fatigue resistance. Absent. In Comparative Example 6, since the compounding amount of the modified butadiene rubber exceeds the upper limit defined in the present invention, the elastic modulus and strength are deteriorated. In Comparative Example 7, since the nitrogen adsorption specific surface area (N ₂ SA) was outside the range defined in the present invention, the low heat build-up was particularly deteriorated.

Claims (3)

5 to 60 carbon blacks having a nitrogen adsorption specific surface area (N ₂ SA) of 20 to 50 m ² / g with respect to 100 parts by mass of diene rubber composed of 30 parts by mass or more of natural rubber and 5 to 70 parts by mass of the modified butadiene rubber described below. A tire side tread characterized by containing a mass part, further containing sulfur and a vulcanization accelerator, and having a sulfur / vulcanization accelerator blending ratio (mass ratio) of 1.75 to 1.9. Rubber composition.
Modified butadiene rubber: A modified butadiene obtained by reacting a compound represented by the following formula (I) or (II) with a polymerization active terminal of a polymer obtained by solution polymerization of a butadiene monomer using an organic active metal catalyst. Rubber.
[Chemical 1]

(In formula (I), A _{1 to} A ₃ are each independently any one of an alkoxyl group, an alkyl group, an aryl group, and hydrogen, and R ₁ includes N, O, S, and P. A linear, alicyclic or aromatic hydrocarbon group having 1 to 30 carbon atoms, and A ₄ and A ₅ each independently represents an organic group which may contain Si, O, N, and S. R ₂ and R ₃ are each independently hydrogen, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 18 carbon atoms, and R ₂ and R ₃ are simultaneously hydrogenated. And m is an integer from 0 to 20 and n is an integer from 2 to 20)
[Chemical 2]

(In the formula (II), _{R 1} is N, O, a hydrocarbon group having 1 to 30 carbon atoms, including S, straight may also include P, and alicyclic or _aromatic, R 2 to R ₆ Are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 18 carbon atoms, and any one of R ₂ and R ₃ can represent hydrogen, and n is an integer of 2 to 20 Is)   The rubber composition for tire side tread according to claim 1, wherein the rubber composition for tire side tread has a Shore A hardness of 50 to 60 at 20 ° C. A pneumatic tire using the rubber composition according to claim 1 for a side tread.