JP4746882B2 - Rubber composition for tire and pneumatic tire comprising the same - Google Patents

Description

  The present invention relates to a rubber composition for tires and a tire comprising the same, which enables production of tires with improved grip performance and wear resistance.

  In recent years, with the improvement of motor performance and higher horsepower, and the development of highways, awareness of safety is increasing. In particular, grip performance represented by acceleration performance and brake performance is an important required characteristic. Conventionally, in order to improve grip performance on a dry and wet road surface of a general road, a method of adding a device to the rubber composition for a tire tread is known.

  As the first method, there is a method using a styrene butadiene copolymer rubber having a high glass transition temperature and a high styrene content. However, in this case, there is a disadvantage that tan δ is lowered as the rubber temperature rises due to running of the vehicle, and grip performance is lowered.

  As a second method, there is a method of ensuring grip performance by increasing tan δ of rubber by highly filling process oil and carbon black. However, in this case, since the fracture resistance and wear resistance of the rubber are lowered, there is a limit to the high filling, and it has been difficult to improve the grip performance at a high level.

  Patent Document 1 discloses a tire rubber composition in which a phenol-based derivative is blended with a specific nitrogen-containing compound in order to improve the grip performance to a high degree. However, the wear resistance has been lowered by improving the grip performance, and both the grip performance and the wear resistance have not been improved.

JP 2001-192503 A

  The present invention improves the disadvantage that tan δ decreases as the tire temperature increases due to running and the grip performance decreases, and enables the production of a tire that improves the grip performance and wear resistance, and a tire rubber composition and It aims at providing the tire which becomes.

The present invention is based on 100 parts by weight of a rubber component containing a styrene butadiene rubber having a styrene content of 20 to 60%.
General formula (1)

(Wherein, R ¹ is formula (a), indicates one of (b) or (c), R ³ and R ⁴ is an alkyl group having 1 to 4 carbon atoms, and R ² is 1 to carbon atoms 4 represents an alkylene group)

And a rubber composition for tires containing 3 to 80 parts by weight of a compound having a melting point of 50 ° C. or higher and a weight average molecular weight of 300 or higher.

  It is preferable that content of the said compound is 5-50 weight part with respect to 100 weight part of rubber components.

  The present invention also relates to a tire comprising the tire rubber composition.

  According to the present invention, a rubber component containing a specific styrene-butadiene rubber and a compound having a structure represented by a specific general formula and having a melting point of 50 ° C. or higher and a weight average molecular weight of 300 or higher are added. Thus, it is possible to provide a tire rubber composition capable of improving wear resistance as well as grip performance, and a tire comprising the same.

  The rubber composition for tires of the present invention comprises a rubber component containing styrene butadiene rubber, and a general formula (1)

(Wherein, R ¹ is formula (a), indicates one of (b) or (c), R ³ and R ⁴ is an alkyl group having 1 to 4 carbon atoms, and R ² is 1 to carbon atoms 4 represents an alkylene group)

It consists of a compound (henceforth a compound A) which has a structure shown by these.

  The styrene content of styrene butadiene rubber (SBR) in the rubber component is 20% or more, preferably 21% or more, more preferably 22% or more. If the styrene content is less than 20%, sufficient grip force required in the low temperature range and the high temperature range cannot be obtained, and the grip performance is insufficient. The styrene content is 60% or less, preferably 50% or less, more preferably 45% or less, still more preferably 35% or less, and particularly preferably 30% or less. When the styrene content exceeds 60%, the hardness of the obtained rubber composition increases, the contact area with the road surface decreases, and high grip performance cannot be obtained. The styrene content refers to the amount of bound styrene in SBR and is calculated by NMR measurement.

  The content of SBR in the rubber component is preferably 3% by weight or more, more preferably 5% by weight or more, and further preferably 50% by weight or more. When the content is less than 3% by weight, the elasticity of the rubber component is lost, the various performances of the tire are inferior, and the tire tends to be plastically deformed by external energy. The content of SBR is particularly preferably 100% by weight.

  As the rubber component, any rubber component such as natural rubber generally used in the tire industry may be added together with SBR.

  Compound A has the general formula (1)

(Wherein, R ¹ is formula (a), indicates one of (b) or (c), R ³ and R ⁴ is an alkyl group having 1 to 4 carbon atoms, and R ² is 1 to carbon atoms 4 represents an alkylene group)

It has the structure shown by.

In the general formula (1), R ¹ is any ^one of the formulas (a), (b), or (c). When R ¹ is not any of the formulas (a), (b) and (c), the interaction between the compound A and the rubber is lowered, and there is a drawback that it is difficult to express energy loss for causing grip.

In the general formula (1), the number of carbon atoms of the alkylene group of R ² is 1-4. When the number of carbon atoms is less than 1, compatibility with rubber deteriorates. On the other hand, when the carbon number exceeds 4, the compound A is not sufficiently dispersed in the rubber composition.

In the general formula (1), the carbon number of the alkyl group of R ³ is 1-4. When the number of carbon atoms is less than 1, the thermal stability of Compound A is impaired. On the other hand, when the carbon number exceeds 4, the compound A and the rubber do not interact with each other due to steric hindrance to the hydroxyl group in the general formula (1).

In the general formula (1), the carbon number of the alkyl group of R ⁴ is 1-4. When the number of carbon atoms is less than 1, the thermal stability of Compound A is impaired. On the other hand, when the carbon number exceeds 4, the compound A and the rubber do not interact with each other due to steric hindrance to the hydroxyl group in the general formula (1).

  Examples of the compound A having the general formula (1) include tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, 3,9-bis [2 -{3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane, etc. Can be given.

  When compound A is added to the rubber component, tan δ can be increased in a high temperature range during running, and the grip performance can be dramatically improved. The increase in tan δ is manifested by the interaction between the agglomerates of Compound A and rubber.

  On the other hand, in the low temperature region, at the start of running, the compound A restricts the mobility of the rubber. However, when the rubber composition is heated by running, the interaction between the compound A and the rubber is expressed. The energy loss (tan δ) of the composition increases.

  Thus, since the rubber temperature of the running tire is very close to the temperature at which tan δ can be increased, the tire rubber composition of the present invention can provide excellent grip performance.

  Further, Compound A has been conventionally used as an antioxidant for resins and the like, and has a property of suppressing degradation of the polymer due to generation of radicals in the polymer chain due to heat or the like. This property suppresses molecular cutting due to wear and improves wear resistance.

  Compound A has a melting point of 50 ° C. or higher, preferably 55 ° C. or higher, more preferably 60 ° C. or higher. When the melting point is less than 50 ° C., the tire is softened, so that sufficient wear resistance cannot be obtained only by the action of the compound A that suppresses molecular cutting. In addition, the melting point of Compound A is preferably 250 ° C. or lower, and more preferably 200 ° C. or lower. When the melting point exceeds 250 ° C., the compound A does not melt at the time of molding the rubber composition, and there is a tendency that tan δ does not increase in the rubber composition.

  Compound A has a weight average molecular weight of 300 or more, preferably 500 or more. If the weight average molecular weight is less than 300, the compatibility with rubber is deteriorated. Moreover, it is preferable that the weight average molecular weight of the compound A is 1500 or less. When the weight average molecular weight exceeds 1500, the compound A tends to not be sufficiently dispersed in the rubber composition.

  The content of Compound A is 3 parts by weight or more, preferably 5 parts by weight or more, more preferably 10 parts by weight or more with respect to 100 parts by weight of the rubber component. If the content is less than 3 parts by weight, the effect of improving tan δ in a high temperature range is small, and the effect of improving grip performance cannot be obtained sufficiently. The content of Compound A is 80 parts by weight or less, preferably 50 parts by weight or less, more preferably 30 parts by weight or less. When the content exceeds 80 parts by weight, various physical properties of the rubber composition are adversely affected, such as a decrease in wear resistance.

  Further, in addition to the above components, the rubber composition for tires of the present invention includes, as necessary, softeners such as carbon black, silica, silane coupling agent, inorganic filler, mineral oil, anti-aging agent, and wax. Additives commonly used in the rubber industry such as a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerating aid can be appropriately blended.

  The compounding amount of carbon black is preferably 10 parts by weight or more, more preferably 20 parts by weight or more with respect to 100 parts by weight of the rubber component. When the blending amount is less than 10 parts by weight, the wear resistance tends to decrease. Further, the blending amount of carbon black is preferably 200 parts by weight or less, and more preferably 150 parts by weight or less. If the blending amount exceeds 200 parts by weight, the processability tends to decrease.

  The tire of the present invention is produced by a usual method using the tire rubber composition of the present invention. That is, the tire rubber composition of the present invention blended with the various chemicals as necessary is extruded in accordance with the shape of the tire member, particularly the tread, at an unvulcanized stage, and is usually used on a tire molding machine. Molded by the method to form an unvulcanized tire. This unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

  The tire of the present invention is particularly preferably a pneumatic tire.

  Next, the present invention will be described in more detail, but the present invention is not limited to these examples.

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
SBR: JBR Corporation SBR1502 (styrene content: 23.5%)
Carbon Black: Show Black N220 (N ₂ SA: 125 m ² / g) manufactured by Showa Cabot Co., Ltd.
Aroma oil: JOMO process X140 manufactured by Japan Energy Co., Ltd.
Stearic acid: Zinc stearate oxide manufactured by Nippon Oil & Fats Co., Ltd .: Zinc Hana No. 1 anti-aging agent manufactured by Mitsui Kinzoku Mining Co., Ltd .: Nocrack 6C (N- (1, 3 -Dimethylbutyl) -N'-phenyl-p-phenylenediamine))
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Compound A: ADK STAB AO-80 (3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1 manufactured by Asahi Denka Kogyo Co., Ltd. -Dimethylethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane) (melting point: 115 ° C., weight average molecular weight: 741)

Examples 1-4 and Comparative Examples 1-2
In accordance with the formulation, sulfur, vulcanization accelerator and compound A shown in Table 1 were kneaded for 5 minutes at 100 ° C. using a Banbury mixer, and then sulfur, vulcanization accelerator and compound A were added. Then, various test rubber compositions were obtained by kneading for 5 minutes at 50 ° C. using a roll machine.

  The obtained various test rubber compositions were press vulcanized at 170 ° C. for 12 minutes to obtain various vulcanizates, which were used in the following tests.

(Lambourn abrasion test)
The amount of wear of the vulcanizate was measured under the conditions of room temperature, applied load of 1.0 kgf, and slip rate of 30% using a Lambourn type wear tester. The reciprocal of the amount of wear was taken, and the index was displayed with Comparative Example 1 being 100. The larger the value, the higher the wear resistance.

(Grip performance)
A tire of size 195 / 65R15 having a tread made of the rubber composition was produced. Using this tire, the vehicle was run on a dry asphalt road test course. The test driver evaluated the stability of control during steering at that time, and the comparative example 1 was set to 100 and displayed as an index. The larger the value, the higher the grip performance on the dry road surface.

  The test results are shown in Table 1.

  In Examples 1 to 4, the wear resistance is improved. In particular, in Examples 1 to 3, it is understood that the grip performance is improved together with the wear resistance.

  On the other hand, in Comparative Example 2, it can be seen that the grip performance is improved, but the wear resistance is low.

Claims (2)

For 100 parts by weight of a rubber component containing a styrene butadiene rubber having a styrene content of 20 to 60%,
Tetrakis [methylene-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane, or
3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5,5] A tire rubber composition containing 5 to 50 parts by weight of undecane . A tire comprising the rubber composition for a tire according to claim 1 .