JP2001123025A - Rubber composition for tire sidewall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for tire sidewalls which shows an excellent dynamic fatigue resistance and is fuel-saving. SOLUTION: A rubber composition for tire sidewalls comprises a random copolymer rubber (A) comprising structural units derived from ethylene, a 3-20C α-olefin and a specific triene compound, a diene rubber (B), carbon black (C) and a vulcanizing agent (D).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a tire sidewall having improved fuel economy without impairing dynamic fatigue resistance such as weather resistance and flex fatigue resistance.

[0002]

BACKGROUND OF THE INVENTION It is said that the role of a sidewall portion in a pneumatic tire is to protect a carcass portion and relieve stress or strain in a tread portion during tire running. Its role is more important than bias tires. Therefore, the characteristics of the sidewall portion required for protection of the carcass portion include weather resistance with respect to ozone degradation, trauma resistance when traveling on a rough road, and adhesion to the carcass portion with respect to the side portion separation problem. on the other hand,
Characteristics of the side wall portion required for stress / strain relaxation of the tread portion include dynamic fatigue resistance and bending resistance. That is, since the pneumatic tire is used under various environments and conditions, the various characteristics as described above are required. Moreover, recently, as road maintenance progresses and radial tires become more widespread, the life of the tires is becoming longer and longer, and among the above-mentioned characteristics, there is an increasing demand for improvement particularly with respect to dynamic fatigue resistance and weather resistance.

[0003] Also, from the viewpoint of appearance, diene rubbers used for tire sidewalls have insufficient weather resistance, and thus are used in combination with an amine antioxidant and a paraffin wax. However, diene rubber products containing an amine-based antioxidant or paraffin-based wax have a tendency to bleed out over time with the amine-based antioxidant or paraffin-based wax, and the surface discolored to red. There was a problem that the value was reduced.

As a prescription not containing an antioxidant or the like, application of EPT having high ozone resistance is known. However, this EPT has a problem in co-vulcanization with a diene rubber.

[0005] In order to solve the above problems, a rubber composition using peroxide vulcanization and comprising natural rubber and EPDM has been developed. However, in such peroxide vulcanization, there is a problem that crack growth resistance required as a property of the tire sidewall is difficult and fatigue resistance is not good.

[0006] The present inventors have significantly improved the vulcanization rate of EPT to give EPT having good co-vulcanizability with diene rubber.
By developing PT, we have conducted intensive research to obtain a rubber composition for tire sidewalls that has excellent dynamic fatigue resistance such as weather resistance and flex fatigue resistance and also has excellent fuel economy. , 8-dimethyl-
By selecting a specific compound such as 1,4,8-decatriene (DMDT), EPT with excellent co-vulcanizability with diene rubber
And that even if the EPT and the diene rubber are co-vulcanized, the excellent dynamic mechanical strength characteristics inherently possessed by the diene rubber are not impaired,
The present invention has been completed. DMDT-EPT is ethylene / propylene / 4-ethylidene-8-methyl-
Compared to 1,7-nonadiene copolymer rubber (EMND-EPT), the vulcanization rate is equivalent and the scorch stability is improved.

[0007]

An object of the present invention is to solve the problems associated with the prior art as described above, and is excellent in dynamic fatigue resistance such as weather resistance and bending fatigue resistance, and is excellent in fuel economy. It is an object of the present invention to provide a rubber composition for a tire sidewall.

[0008]

SUMMARY OF THE INVENTION The rubber composition for a tire sidewall according to the present invention comprises ethylene, an α-olefin having 3 to 20 carbon atoms, and a structural unit derived from a triene compound represented by the following general formula [1]. A random copolymer rubber (A), a diene rubber (B), a carbon black (C), and a vulcanizing agent (D). , (I) ethylene and 3 carbon atoms
The molar ratio (ethylene / α-olefin) to the α-olefin of from 20 to 20 is in the range of 99/1 to 30/70, and (i
i) The content of the structural unit derived from the triene compound is 0.1 to 30 mol%, and (iii) the intrinsic viscosity [η] measured in decalin at 135 ° C. is in the range of 0.1 to 10 dl / g. A rubber composition for a tire tread;

[0009]

Embedded image

[In the formula [1], R ¹ and R ² each independently represent a hydrogen atom, a methyl group or an ethyl group, and R ³ and R ⁴ each independently represent a methyl group or an ethyl group. ]

[0011]

DETAILED DESCRIPTION OF THE INVENTION The rubber composition for a tire sidewall according to the present invention will be specifically described below.

The rubber composition for a tire sidewall according to the present invention comprises a specific random copolymer rubber (A), a diene rubber (B), a carbon black (C), and a vulcanizing agent (D).
And a vulcanizable rubber composition containing

Random copolymer rubber (A) The random copolymer rubber (A) used in the present invention comprises ethylene, an α-olefin having 3 to 20 carbon atoms, and a structural unit derived from a triene compound. Become.

Specific examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene,
Methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl
-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1
-Hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-
Hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-
Octadecene, 1-eicosene and the like. Among them, propylene, 1-butene, 1-hexene and 1-octene are preferably used.

These α-olefins can be used alone or in combination of two or more. The structural unit derived from the triene compound has the following general formula [1]
Is represented by

[0016]

Embedded image

[In the formula [1], R ¹ and R ² each independently represent a hydrogen atom, a methyl group or an ethyl group, and R ³ and R ⁴ each independently represent a methyl group or an ethyl group. ]

Among the triene compounds represented by the above formula [1], a compound in which R ³ and R ⁴ are both methyl groups is preferable. A random copolymer rubber obtained by using such a triene compound as a monomer material is It is particularly excellent in the balance between vulcanization rate and scorch characteristics.

Specific examples of the triene compound represented by the above formula [1] include the following compounds.

Embedded image In addition, these triene compounds are disclosed in Japanese Patent Application No. 11-1464.
It can be produced by the method described in No. 29.

Among the above triene compounds, 4,8-dimethyl-1,4,8-decatriene (hereinafter abbreviated as DMDT), which is the first exemplified, is preferable. The triene compound represented by the formula [1] may be a mixture of a trans form and a cis form, or may be a trans form alone or a cis form alone.

The triene compound represented by the formula [1] is obtained by reacting a compound having a conjugated diene represented by the following formula [2] with ethylene in the presence of a catalyst comprising a transition metal compound and an organoaluminum compound. Can be manufactured.

[0022]

Embedded image

[0023] (wherein ^{[2], R 1, R} 2, R 1 in R ³ and R ⁴ in general formula described above, respectively ^{[1], R 2, R} 3
And R ⁴ are the same. In the random copolymer rubber (A) used in the present invention, the structural units derived from the monomers of the ethylene, α-olefin and triene compounds as described above are randomly arranged and bonded to form a triene rubber. It has a branched structure due to the compound, and the main chain has a substantially linear structure.

The fact that the copolymer rubber has a substantially linear structure and substantially does not contain a gel-like crosslinked polymer means that the copolymer rubber is dissolved in an organic solvent and the insoluble matter is substantially reduced. It can be confirmed by not including it. For example, when the intrinsic viscosity [η] is measured, it can be confirmed that the copolymer rubber is completely dissolved in decalin at 135 ° C.

In such a random copolymer rubber (A), the structural unit derived from the triene compound has a structure substantially represented by the following formula [3].

[0026]

Embedded image

[0027] (wherein ^{[2], R 1, R} 2, R 1 in R ³ and R ⁴ in general formula described above, respectively ^{[1], R 2, R} 3
And R ⁴ are the same. The fact that the structural unit derived from the triene compound has the above structure can be confirmed by measuring the ¹³ C-NMR spectrum of the copolymer.

The random copolymer rubber (A) used in the present invention, for example, ethylene / propylene / 4,8-dimethyl-1,4,8-decatriene (DMDT) copolymer rubber is prepared by using the existing ethylene / propylene Compared with 5-ethylidene-2-norbornene (ENB) copolymer rubber, the vulcanization rate is about twice as fast and almost the same as the diene rubber, so that the diene rubber inherently has The initial physical properties of the tire tread can be maintained without impairing the excellent dynamic mechanical strength characteristics.

The random copolymer rubber (A) used in the present invention has the following composition and properties. (I) This random copolymer rubber has a molar ratio of ethylene to an α-olefin having 3 to 20 carbon atoms (ethylene /
α-olefin) is in the range of 60/40 to 90/10, preferably 70/30 to 80/20.

It is preferable in terms of rubber elasticity that the molar ratio of ethylene to α-olefin having 3 to 20 carbon atoms be within this range. If the ratio is less than 60/40, the glass transition point of the random copolymer shifts to a high temperature, and rubber elasticity is lost. In addition, ethylene and carbon atoms 3 to
If the molar ratio of the α-olefin to 20 exceeds 90/10, the random copolymer becomes a resinous substance, and rubber elasticity is lost, which is not preferable.

(Ii) The content of the structural unit derived from the triene compound of the random copolymer rubber (A) is 0.1 to
It is 30 mol%, preferably 0.5 to 8 mol%, more preferably 0.5 to 5 mol%. When the triene compound content of the random copolymer rubber is within the above range, the heat resistance is excellent and the vulcanization rate is high.

(Iii) The random copolymer rubber (A)
Has an intrinsic viscosity [η] of 0.1 to 10 dl / g, preferably 2.0 to 5.0 dl, measured in decalin at 135 ° C.
/ G.

When a random copolymer rubber (A) having an intrinsic viscosity [η] in the above range is used, the obtained rubber composition is required to have excellent blending properties with a diene rubber and to be used as a tire tread. High mechanical strength.

In the present invention, the random copolymer rubber (A) is used in an amount of 20 to 80 parts by weight based on 100 parts by weight of the total of the random copolymer rubber (A) and the diene rubber (B). It is preferably used in a proportion of 20 to 70 parts by weight, more preferably 20 to 60 parts by weight. (A) and (B)
Is preferably in this range from the viewpoint of the mechanical strength of the tire.

The above random copolymer rubber (A)
Can be obtained by copolymerizing ethylene, an α-olefin having 3 to 20 carbon atoms, and a structural unit derived from the triene compound represented by the general formula [1] in the presence of a catalyst.

As such a catalyst, a Ziegler catalyst comprising a transition metal compound such as vanadium (V), zirconium (Zr), or titanium (Ti) and an organic aluminum compound (organic aluminum oxy compound) can be used.

In the present invention, [a] a catalyst comprising a soluble vanadium compound and an organoaluminum compound, or [b] a metallocene compound of a transition metal selected from Group IVB of the periodic table, and an organoaluminum oxy compound or an ionized ionic compound A catalyst comprising a compound is particularly preferably used.

In the present invention, the catalyst [a] (a catalyst comprising a soluble vanadium compound and an organoaluminum compound) or the catalyst [b] (a metallocene compound of a transition metal selected from Group IV of the periodic table) and an organic Ethylene in the presence of an aluminum oxy compound or a catalyst comprising an ionized ionic compound) and ethylene having an α of 3 to 20 carbon atoms.
-An olefin and a structural unit derived from a triene compound are usually copolymerized in a liquid phase.

In this case, a hydrocarbon solvent is generally used, but an α-olefin such as propylene may be used as the solvent. Specific examples of such hydrocarbon solvents include pentane, hexane, heptane, octane, decane, dodecane, aliphatic hydrocarbons such as kerosene and halogen derivatives thereof, cyclohexane, methylcyclopentane,
Alicyclic hydrocarbons such as methylcyclohexane and halogen derivatives thereof, aromatic hydrocarbons such as benzene, toluene and xylene, and halogen derivatives such as chlorobenzene are used.

These solvents may be used in combination.
The copolymerization of ethylene, an α-olefin having 3 to 20 carbon atoms and a structural unit derived from a triene compound may be carried out by either a batch method or a continuous method. When the copolymerization is carried out by a continuous method, the above-mentioned catalyst is used in the following concentration.

In the present invention, when the above-mentioned catalyst [a], that is, a catalyst comprising a soluble vanadium compound and an organoaluminum compound is used, the concentration of the soluble vanadium compound in the polymerization system is usually 0.01 to 5%. Mmol / liter (polymerization volume), preferably 0.05 to 3 mmol / liter. This soluble vanadium compound is desirably supplied at a concentration of 10 times or less, preferably 1 to 7 times, more preferably 1 to 5 times the concentration of the soluble vanadium compound present in the polymerization system.

The organoaluminum compound has a ratio of aluminum atoms to vanadium atoms in the polymerization system (A
1 / V), and is supplied in an amount of 2 or more, preferably 2 to 50, more preferably 3 to 20.

The catalyst [a] comprising a soluble vanadium compound and an organoaluminum compound is usually diluted with the above-mentioned hydrocarbon solvent and / or a liquid α-olefin having 3 to 20 carbon atoms and a branched polyene compound. Supplied. At this time, the soluble vanadium compound is desirably diluted to the concentration described above, and the organoaluminum compound is diluted to, for example, 50% of the concentration in the polymerization system.
It is desirable to adjust the concentration to an arbitrary concentration of 2 times or less and supply it to the polymerization system.

In the present invention, when a catalyst [b] comprising a metallocene compound and an organic aluminum oxy compound or an ionized ionic compound (also referred to as an ionic ionized compound or an ionic compound) is used, a polymerization system is used. The concentration of the metallocene compound in is usually 0.1.
0.0005-0.1 mmol / liter (polymerization volume),
Preferably it is 0.0001-0.05 mmol / l.

The organic aluminum oxy compound is
It is supplied in an amount of 1 to 10,000, preferably 10 to 5,000 in terms of the ratio of aluminum atoms to the metallocene compound in the polymerization system (Al / transition metal).

In the case of the ionized ionic compound, the molar ratio of the ionized ionic compound to the metallocene compound in the polymerization system (ionized ionic compound / metallocene compound) is 0.5 to 20, preferably 1 to 10. Supplied.

When an organoaluminum compound is used, it is generally used in an amount of about 0 to 5 mmol / l (polymerization degree), preferably about 0 to 2 mmol / l.

In the present invention, ethylene, an α-olefin having 3 to 20 carbon atoms and a structural unit derived from a triene compound are copolymerized in the presence of a catalyst [a] comprising a soluble vanadium compound and an organoaluminum compound. When it is carried out, the copolymerization reaction is usually carried out at a temperature of -50C to 10C.
The reaction is carried out at 0 ° C., preferably at −30 ° C. to 80 ° C., more preferably at −20 ° C. to 60 ° C., and at a pressure of 5 MPa or less, preferably 2 MPa or less.

In the present invention, ethylene, an α-olefin having 3 to 20 carbon atoms and a triene compound are derived in the presence of a catalyst [b] comprising a metallocene compound and an organic aluminum oxy compound or an ionized ionic compound. When copolymerizing with a structural unit, the temperature of the copolymerization reaction is usually from -20 ° C to 150 ° C, preferably 0 ° C.
C. to 120.degree. C., more preferably 0.degree. C. to 100.degree. C., and a pressure of 8 MPa or less, preferably 5 MPa or less.

The reaction time (average residence time when the copolymerization is carried out by a continuous method) varies depending on conditions such as the catalyst concentration and the polymerization temperature, but is usually 5 minutes to 5 hours, preferably 10 minutes. ~ 3 hours.

In the present invention, ethylene, C 3 -C 2
The structural unit derived from the α-olefin and the triene compound of 0 is supplied to the polymerization system in such an amount as to obtain the random copolymer rubber having the above specific composition. Further, upon copolymerization, a molecular weight regulator such as hydrogen may be used.

As described above, ethylene and carbon atoms 3
When structural units derived from α-olefins and triene compounds of from 20 to 20 are copolymerized, a random copolymer rubber is usually obtained as a polymerization liquid containing the same. This polymerization liquid is
It is processed by a conventional method to obtain a random copolymer rubber.

The method for preparing the random copolymer rubber (A) [unsaturated ethylene copolymer] as described above is described in detail in Japanese Patent Application No. 10-323222.

Diene Rubber (B) The diene rubber (B) used in the present invention is not particularly limited, and may be a rubber usually used for a tire tread. Specifically, natural rubber (NR), isoprene Rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR) and the like. Above all, isoprene-based rubbers having balanced mechanical strength, that is, natural rubber (NR), styrene-butadiene rubber (SB)
R) Isoprene rubber (IR) is preferably used.

These diene rubbers can be used alone or in combination. In the present invention, the diene rubber (B) is based on 100 parts by weight of the total amount of the random copolymer rubber (A) and the diene rubber (B).
20 to 80 parts by weight, preferably 30 to 70 parts by weight, more preferably 40 to 60 parts by weight.

Carbon Black (C) The carbon black (C) used in the present invention includes:
There is no particular limitation, as long as it is carbon black normally used for tire treads. Specifically, SRF, GP
And carbon blacks such as F, FEF, HAF, ISAF, SAF, FT, and MT.

In the present invention, the carbon black (C) is used in an amount of 20 to 12 parts by weight based on 100 parts by weight of the total of the random copolymer rubber (A) and the diene rubber (B).
0 parts by weight, preferably 30 to 100 parts by weight, more preferably 40 to 90 parts by weight. When the carbon black (C) is used in the above ratio, a rubber composition capable of providing a tire tread excellent in wear resistance and dynamic fatigue resistance is obtained.

Vulcanizing Agent (D) The vulcanizing agent (D) preferably used in the present invention is sulfur or a sulfur compound.

Specific examples of the sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur. As sulfur compounds,
Specific examples include sulfur chloride, sulfur dichloride, polymer polysulfide, and the like. Sulfur compounds which release active sulfur at the vulcanization temperature and vulcanize, for example, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, dipentamethylenethiuram tetrasulfide and the like can also be used.

In the present invention, powdered sulfur is preferably used. In the present invention, the vulcanizing agent (D) has a total amount of 1 of the random copolymer rubber (A) and the diene rubber (B) of 1%.
Usually 0.5 to 10 parts by weight, preferably 1 to 10 parts by weight, more preferably 1.0 to 5.0 parts by weight with respect to 00 parts by weight.
Used in parts by weight.

Rubber composition for tire sidewall The rubber composition for tire sidewall according to the present invention comprises the above-mentioned random copolymer rubber (A), diene rubber (B), carbon black (C) and rubber black. Sulfurizing agent (D)
It contains.

The tire sidewall obtained from the rubber composition for a tire sidewall according to the present invention has excellent fuel efficiency. Whether or not the fuel efficiency is excellent in the present invention can be confirmed by determining whether the value of the loss tangent (tan δ) is low or high. The fuel efficiency is better as the value of the loss tangent is smaller. When strain is applied to the rubber material, the calorific value is proportional to the square of the input strain, and the frequency and tan
It is theoretically known that it is proportional to δ. The fuel efficiency is lost as the force transmitted to the tire is consumed as heat instead of rolling force. Therefore, as the material of the tire sidewall, the smaller the tan δ related to heat generation, the lower the fuel efficiency of the tire.

The rubber composition for a tire sidewall according to the present invention can be produced by employing a known rubbery polymer mixing method such as a mixing method using a mixer such as a Banbury mixer. In addition, in the present invention, at the time of rubber compounding, in addition to the random copolymer rubber (A), the diene rubber (B), the carbon black (C) and the vulcanizing agent (D), a normal rubber compounding agent is used. It can be used in a range that does not impair the object of the present invention.

Examples of such a compounding agent include a softening agent; a rubber reinforcing agent such as finely divided silica; a filler such as light calcium carbonate, heavy calcium carbonate, talc, clay and silica; a tackifier; a wax; Resins; zinc oxide; antioxidants; antiozonants; processing aids and vulcanizing activators. These compounding agents can be used alone or in combination of two or more.

The vulcanized product of the rubber composition for a tire sidewall according to the present invention comprises the above-mentioned random copolymer rubber (A), diene rubber (B), carbon black (C), vulcanizing agent ( D) and, if necessary, other compounding agents can be obtained by adopting a usual vulcanization method of heating and vulcanizing at a temperature of 150 to 200 ° C. for 5 to 60 minutes.

[0066]

The rubber composition for a tire sidewall according to the present invention contains a specific ethylene / α-olefin / triene copolymer rubber, a diene rubber, carbon black, and a vulcanizing agent. Therefore, it is possible to provide a tire sidewall having excellent dynamic fatigue resistance such as weather resistance and bending fatigue resistance, and also having excellent fuel economy.

Hereinafter, the present invention will be described with reference to Examples.
The present invention is not limited to these examples. In addition, the test method performed about the vulcanized rubber in an Example and a comparative example is as follows.

[1] Physical Properties Test of Unvulcanized Rubber The physical properties test of the unvulcanized rubber was performed in accordance with JIS K6300. The scorch stability was measured using a Mooney viscometer (model SMV-202) manufactured by Shimadzu Corporation at 125 ° C. and the change in Mooney viscosity was measured at t ₅ [min].
As a guide. The t ₅ indicates the longer scorch that stability is good. The vulcanization rate was measured by measuring the change in torque at 160 ° C. using a rotorless rheometer (model MDR2000) manufactured by Monsanto Co.
0) was obtained and used as a guide. The shorter the tc (90), the higher the vulcanization rate.

[2] Dynamic Viscoelasticity Test The dynamic viscoelasticity test was conducted on a 2 mm thick vulcanized rubber sheet using a viscoelasticity tester (model RDS-
Using 2), the loss tangent tan δ (index of vibration damping property) at a measurement temperature of 0 ° C., a frequency of 10 Hz, and a distortion of 1%
Was measured.

The loss tangent (tan δ) at 0 ° C.
Specimens before and after an air heating aging test (100 ° C., 48 hours) according to IS K 6257 (1993) were obtained, and the rate of change was further obtained.

[3] Tensile test A vulcanized rubber sheet was punched out and JIS K6251 (199)
No. 3 dumbbell test piece described in (3 years), and using this test piece, a measurement temperature of 25 ° C. and a tensile speed of 50 were applied in accordance with the method specified in JIS K 6251, Paragraph 3.
A tensile test was performed under the conditions of 0 mm / min, 100% modulus (M100), 200% modulus (M200),
100% modulus (M300), tensile stress at break T _B and tensile elongation at break E _B were measured.

[4] Hardness Test The hardness test was performed according to JIS K 6253 (1993), and the spring hardness H _A (Shore A hardness) was measured.

[5] Dynamic Tensile Fatigue Test (Ueshima Fatigue Testing Machine) A vulcanized rubber sheet was punched out to prepare a No. 1 type dumbbell test piece described in JIS K6251, and the longitudinal center of the test piece was prepared. Was wound 2 mm. Of the nine test pieces obtained in this way, the elongation rate was 50 for three of the three test pieces.
%, The specimen was subjected to elongation fatigue under the conditions of a set temperature of 23 ° C. and a rotation speed of 300 rpm. The elongation rate is 100
% And 145%, a dynamic tensile fatigue test was performed in the same manner.

[6] Crack Growth Test (Dematcher Flex Test) In the crack growth test, resistance to crack growth was examined using a dematcher tester in accordance with ASTM D813. That is, the number of bends until a crack was generated and the number of bends until the test piece was completely cut were measured (measurement temperature 40 ° C.,
Rotation speed 300 rpm).

Table 1 shows the random copolymer rubber (EPT) used in the examples and comparative examples.

[0076]

[Table 1] (Note) DMDT-EPT: Ethylene propylene 4,8-dimethyl-1,4,8-decatriene copolymer rubber ENB-EPT: Ethylene propylene 5 -ethylidene-2
-Norbornene copolymer rubber

[0077]

Examples 1 to 4 [Production of vulcanized rubber] The above-mentioned ethylene / propylene / 4,8-dimethyl-1,4,8-decatriene copolymer rubber (DMD) was used as a random copolymer rubber (A).
T-EPT) and SBR15 as a diene rubber (B).
02 and a blend ratio (SBR / DMDT-EPT) of 70
/ 30 according to Table 2 to obtain an unvulcanized compounded rubber.

At the time of this compounding, in addition to the above copolymer rubber (DMDT-EPT) and SBR, zinc white,
Stearic acid, carbon black [trade name: Carbon Black N330, manufactured by Asahi Carbon Co., Ltd.], vulcanization accelerator [trade name: Suncellar CM, Sanshinko Chemical Industry Co., Ltd.]
8 inch roll (front roll /
(Roll: 100 ° C./100° C.) to obtain a compounded rubber.

[0079]

[Table 2]

The compounded rubber obtained as described above is sheeted out, and tc is pressed by a press heated to 160 ° C.
(90) +3 minutes of heating and pressurization to prepare a vulcanized sheet having a thickness of 2 mm, and the above dynamic viscoelasticity test, tensile test, hardness test, dynamic tensile fatigue test and crack growth test were performed.

Table 3 shows the results.

[0082]

Comparative Example 1 In Example 1, DMDT-EPT-1 was used.
A vulcanized sheet having a thickness of 2 mm was prepared in the same manner as in Example 1 except that ENB-EPT was used instead of the above, and the above dynamic viscoelasticity test, tensile test, hardness test, elongation fatigue test, and crack growth were performed. The test was performed.

Table 3 shows the results.

[0084]

[Table 3]

The rubber compositions comprising DMDT-EPT in Examples 1 to 3 are excellent in dynamic fatigue resistance and crack growth resistance, low in loss tangent (tan δ), and excellent in fuel efficiency of tires.

On the other hand, ENB-E in Comparative Example 1
The rubber composition composed of PT is different from those in Examples 1 to 3,
Poor dynamic fatigue resistance, crack growth resistance and low fuel consumption.

Claims (2)

[Claims] 1. A random copolymer rubber (A) comprising ethylene, an α-olefin having 3 to 20 carbon atoms, and a structural unit derived from a triene compound represented by the following general formula [1]: The random copolymer rubber (A) comprises (i) ethylene and 3 to 20 carbon atoms (B), a carbon black (C), and a vulcanizing agent (D). The molar ratio with the α-olefin (ethylene / α-olefin) is in the range of 99/1 to 30/70, and (ii) the content of the structural unit derived from the triene compound is 0.1 to 30 mol%. Yes, (iii) 135 ° C
Intrinsic viscosity [η] measured in decalin is 0.1 to 10 d
a rubber composition for a tire sidewall, which is in the range of 1 / g; [In the formula [1], R ¹ and R ² are each independently a hydrogen atom, a methyl group or an ethyl group, and R ³ and R ⁴ are each independently a methyl group or an ethyl group. ] 2. The content of the random copolymer rubber (A) is 20 to 80 parts by weight based on 100 parts by weight of the total of the random copolymer rubber (A) and the diene rubber (B). The rubber composition for a tire sidewall according to claim 1, wherein the content of the diene rubber (B) is 20 to 80 parts by weight.