JP2609623B2 - Pneumatic tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire excellent in fracture resistance, abrasion resistance and low heat generation.

[Prior art] Conventionally, when improving the rubber of the tread of a pneumatic tire, for example, a rubber material selection point (Japanese Standards Association, 19
According to the first edition published on August 10, 1979, pages 107 to 130, rubber materials for tires, selection of rubber materials according to the use and improvement purpose of tires, mixing of rubber materials and carbon black, softener It is described that the type and amount of the product are appropriate. For example, natural rubber is used to improve low heat build-up and fracture resistance, and styrene-butadiene rubber is used to improve fracture resistance such as abrasion resistance and cut resistance. It is known to use butadiene rubber to improve heat build-up. Depending on the purpose of improvement, these rubber materials are mixed in an appropriate amount. It is also known that the wear resistance is improved by blending carbon black into a rubber material, particularly by blending a small and large amount of carbon black particles.

Also, The Rubber Association of Japan, Vol. 56, No. 7, p. 418 (198
According to the publication of Butadiene Rubber, a butadiene rubber having a wide molecular weight distribution is disclosed in order to improve tack (adhesion) and green strength (strength of unvulcanized rubber).

JP-A-59-45337 discloses that the ratio between the weight average molecular weight and the number average molecular weight is 5 or more in order to improve the green strength of butadiene rubber.

On the other hand, as a rubber composition for a sidewall of a pneumatic tire, a mixture of natural rubber, butadiene rubber, and styrene-butadiene rubber has been conventionally used. However, in recent years, the mixing ratio of butadiene rubber has increased in order to improve bending durability, and now natural rubber and butadiene rubber are dominant in the market, and the mixing ratio of butadiene rubber is 50% or more. Is also increasing.

[Problems to be Solved by the Invention] However, in order to improve the low heat build-up, abrasion resistance, and fracture resistance of tread rubber of a pneumatic tire, a large amount of butadiene rubber is used in a mixture of natural rubber and butadiene rubber. When mixed, the wear resistance is improved, but the fracture resistance such as crack resistance deteriorates. When the mixing ratio of the natural rubber is increased, the crack resistance is improved, but the wear resistance is reduced. As described above, in the related art, there is a problem that when one characteristic is attempted to be improved, the other characteristic is deteriorated.

On the other hand, in order to improve the bending durability of the sidewall rubber of the pneumatic tire, in a mixture of natural rubber and butadiene rubber, when a large amount of butadiene rubber is mixed,
There is a problem that the fracture resistance such as cut resistance is reduced.

Accordingly, an object of the present invention is to provide a pneumatic tire excellent in all of the fracture resistance, abrasion resistance and low heat generation required for tread rubber and sidewall rubber.

[Means for Solving the Problems] An object of the present invention is to provide (a) (a) a lanthanum series rare earth element compound and (b) a general formula AlR ¹ R ² R ³ (where R ¹ , R ² and R ³ is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, except that all are hydrogen atoms), and if necessary, (c) Lewis acid and / or (d) In a polymer obtained by polymerizing 1,3-butadiene in an inert organic solvent in the presence of a catalyst containing a Lewis base, (e) a compound represented by the general formula R ′ _n MX _4-n (where R ′ is carbon An alkyl group or an aryl group of the formulas 1 to 20, M is a tin atom or a germanium atom, X is a halogen atom, and n is an integer of 1 to 3). Contains 70% or more of cis 1,4 bonds and has a weight average molecular weight of 300,000 to 12 0,000, weight average molecular weight (w) and number average molecular weight (n)
Butadiene rubber having a ratio (w / n) of 3 to 15
It is formed from a rubber composition containing 0 to 0% by weight and (B) 90 to 0% by weight of at least one diene rubber selected from the group consisting of natural rubber, isoprene rubber, styrene-butadiene rubber and butadiene rubber. This is achieved by a pneumatic tire having rubber on the tread and / or sidewall.

The lanthanum series rare earth catalyst used in the present invention includes a lanthanum series rare earth metal compound (hereinafter, referred to as “component (a)”) and (b) an organoaluminum compound represented by the general formula AIR ¹ R ² R ³ (hereinafter, referred to as “AIR ¹ R ² R ³ ”). (Referred to as "component (b)"). This may contain (c) the Lewis acid (hereinafter referred to as “component (c)”) and / or (d) Lewis base (hereinafter referred to as “component (d)”) as necessary.

First, as the lanthanum series rare earth element compound as the component (a), a compound represented by the general formula LnY ₃ is suitably used. Here, Ln is a lanthanum series rare earth element having an atomic number of 57 to 71 in the periodic table, among which cerium, lanthanum, praseodymium, neodymium and gadolinium are preferable, and neodymium is particularly preferable because it is easily available industrially.

These rare earth elements may be a mixture of two or more kinds.

Y is in the form of alkyl, alkoxide, thioalkoxide, amide, phosphate, phosphite, halogen and carboxylate, and alkoxide, halide and carboxylate are particularly preferred.

Among them, the alkyl type compounds of the lanthanum series rare earth element is represented by LnR _'3, the R can be exemplified benzyl group, a phenyl group, butyl group, cyclopentadienyl group.

The alcohol-type compound (alkoxide) is represented by the general formula Ln (OR) ₃ (wherein Ln and R are the same as described above), and preferred alcohols are 2-ethyl-hexyl alcohol, oleyl alcohol, stearyl alcohol, and phenol. And benzyl alcohol.

The thioalcohol type compound (thioalkoxide) is represented by the general formula Ln (SR) ₃ (wherein Ln and R are the same as described above), and preferable thioalcohols include thiophenol.

The amide type compound (amide) is represented by the general formula Ln (NR) ₃
Wherein Ln and R are the same as described above, and preferred amines include dihexylamine and dioctylamine.

As the rare earth element phosphate, a general formula (In the formula, Ln is the same as described above; R ⁵ and R ⁶ are the same as the above R.), preferably, tris (dihexyl phosphate) neodymium, tris (diphenyl phosphate) neodymium, and the like.

As the phosphite of the rare earth element, a general formula (In the formula, Ln is the same as above. R ⁵ and R ⁶ are the same as the above R.), preferably tris (dihexyl phosphite) neodymium, tris [di (2-ethylhexyl phosphite)]
Neodymium and the like.

The halogen type compound is represented by the general formula LnX _'3, as is preferably a halogen atom chlorine atom, a bromine atom, an iodine atom.

As the carboxylate of the rare earth element, a general formula (RC
OO) ₃ Ln, wherein R is a hydrocarbon group having 1 to 20 carbon atoms, preferably a saturated or unsaturated alkyl group, and a linear, branched or cyclic, carboxyl group Is bonded to a primary, secondary or tertiary carbon atom. Specifically, preferred carboxylic acids include octanoic acid, 2-ethyl-hexanoic acid, oleic acid, stearic acid, benzoic acid, and naphthenic acid.

Specific examples of the component (a) include neodymium trichloride and didim trichloride (neodymium 72% by weight, lanthanum 20
Weight percent, praseodymium 8 weight% mixture of rare earth metal trichloride, 2-ethylhexanoic acid / neodymium, 2-ethylhexalic acid / didim, naphthenic acid / neodymium, 2,2-
Neodymium diethylhexanoate, neodymium trimethacrylate, neodymium trimethacrylate polymer, and the like.

The organoaluminum compound as the component (b) has the general formula AlR ¹ R ² R ³ (wherein R ¹ R ² and R ³ are a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, all of which are hydrogen) Excluding the case of an atom), specifically, trimethylaluminum, triethylaluminum, triisopropylaluminum, tributylaluminum, triisobutylaluminum, trihexylaluminum, tricyclohexylaluminum, diisobutylaluminum hydride, diethylaluminum Hydride, dipropylaluminum hydride, ethylaluminum dihydride, propylaluminum dihydride, isobutylaluminum dihydride and the like.

As the Lewis acid as the component (c), for example, a general formula Al
A halogenated aluminum compound represented by R ⁴ _m X _3-m (wherein, R ⁴ is a hydrocarbon group having 1 to 8 carbon atoms, m is an integer of 0 to 3 and X is the same as described above), a halogen element, and And halides such as tin and titanium.

Among them, particularly preferred are dimethylaluminum chloride, diethylaluminum chloride, dibutylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum sesquibromide, ethylaluminum dichloride, and bromides and iodide compounds thereof.

Examples of the Lewis base as the component (d) include acetylacetone, tetrahydrofuran, pyridine, N, N-dimethylformamide, thiophene, diphenyl ether, triethylamine, organic phosphorus compounds, and monohydric or dihydric alcohols.

The composition of the lanthanum series rare earth metal catalyst used in the present invention is usually as follows.

Component (b) / component (a) (molar ratio) is from 10 to 150, preferably from 15 to 100. If it is less than 10, the polymerization activity is low,
On the other hand, if it exceeds 150, the effect on polymerization activity is small, and it is economically disadvantageous.

Component (c) / component (a) (molar ratio) is 0 to 6,
Preferably it is 0.5 to 5.0, and when it exceeds 6, the polymerization activity becomes low.

Further, component (d) / component (a) (molar ratio) is 0 to
It is preferably 20 to 1, more preferably 1 to 15. If it exceeds 20, the polymerization activity is undesirably low.

As the catalyst component, (a), (b), (c),
In addition to the component (d), if necessary, a conjugated diene is added to the component (a).
It may be used in a proportion of 0 to 50 mol per 1 mol of the lanthanide series rare earth element compound as a component. The conjugated diene used for preparing the catalyst is isoprene, 1,3-butadiene, 1,3-
Pentadiene or the like is used. Although a conjugated diene as a catalyst component is not essential, the combined use thereof further improves the catalytic activity of the catalyst component.

To prepare the catalyst, for example, (a)-
The component (d) is further reacted with a conjugated diene, if necessary. At that time, the order of addition of each component may be arbitrary. These components are preferably mixed, reacted, and aged in advance for the purpose of improving the polymerization activity and shortening the polymerization initiation induction period.However, during the polymerization, the catalyst components may be added directly to the solvent and the monomer in sequence. .

Examples of the polymerization catalyst include inert organic solvents, for example, aromatic hydrocarbon solvents such as benzene, toluene, and xylene; aliphatic hydrocarbon solvents such as n-pentane, n-hexane, n-butane, and cyclohexane; and methylcyclohexane. Alicyclic hydrocarbon solvents such as pentane and cyclohexane, halogenated hydrocarbon solvents such as ethylene dichloride and chlorobenzene, and mixtures thereof can be used.

The polymerization temperature is usually -20 ° C to 150 ° C, preferably 30 ° C.
~ 120 ° C. The polymerization reaction may be a batch type or a continuous type.

Incidentally, the monomer temperature in the solvent is usually 5 to 50% by weight,
Preferably it is 10 to 35% by weight.

In addition, in order to prevent the deactivation of the lanthanum series rare earth metal catalyst and the living polymer of the present invention in order to produce a living polymer, mixing of a compound having a deactivating effect such as oxygen, water or carbon dioxide gas into the polymerization system is minimized. Care must be taken to eliminate them.

In the present invention, during the polymerization of 1,3 butadiene in an inert organic solvent using a lanthanum series rare earth metal catalyst in this way, taking advantage of the high living polymerizability of the catalyst system, the polymer growth terminal is mainly used. (B) chain transfer to an organoaluminum compound to add an organoaluminum compound to the polymer terminal, and subsequently react and modify a specific organometallic halide at the obtained polymer terminal to obtain a functional group of the polymer. A new polymer is obtained by introducing a group.

This modification has the effect of improving wear resistance, heat generation characteristics, and mechanical characteristics.

In the present invention, the organometallic halide to be reacted after the production of the 1,3-butadiene polymer (hereinafter referred to as “component (e)”) is represented by the following general formula.

R ′ _n MX _4-n (wherein, R ′ is an alkyl or aryl group having 1 to 20 carbon atoms, M is a tin atom or germanium atom, X is the same as described above, and n is an integer of 1 to 3) There is a "(e)
Here, when M is a tin atom, examples of the component (e) include triphenyltin chloride, tributyltin chloride, tri-isopropyltin chloride, diphenyltin dichloride, dioctyltin dichloride, dibutyltin dichloride, and phenyltin. Trichloride, butyltin trichloride and the like.

When M is a germanium atom, the component (e) includes, for example, triphenylgermanium chloride,
Compounds such as dibutylgermanium dichloride, diphenylgermanium dichloride, butylgermanium trichloride and the like can be mentioned.

 These components (e) may be used in an optional ratio.

The amount of the component (e) to be used relative to the component (a) is (component (e) / component (a) (molar ratio) = 0.1 to 100, more preferably 0.5 to 50. In addition, there is no effect of improving abrasion resistance. On the other hand, use of more than 100 is unnecessary, and in some cases, toluene-insoluble matter (gel) is generated, which is not preferable.

This coupling reaction is carried out at a temperature of 160 ° C. or less, preferably 0 ° C.
0.1 to 10 hours with stirring at a temperature of ~ 130 ° C, preferably 0.2
It is desirable to carry out for up to 5 hours.

After completion of the reaction, steam may be blown into the polymer solution to remove the solvent, or a poor solvent such as methanol may be added to solidify the modified polymer, and then dried under a hot roll or under reduced pressure to obtain a polymer. it can. The polymer can also be obtained by directly removing the solvent from the polymer solution under reduced pressure. Thus, the butadiene rubber used in the present invention is obtained.

Further, the butadiene rubber obtained by the polymerization method is caused by Sn-φ bond, for example, by an infrared absorption spectrum.
700 cm ^-1 vicinity absorption, due absorption around 770 cm ^-1 attributable to Sn-CH ₃ bonds, it is possible to confirm the structure.

On the other hand, when diphenyltin dichloride is used as the component (e), Fourier Transform NMR spectrometer (Fourier Transform NMR)
Spectrometer; hereinafter, referred to as “FT-NMR”), the structure of which can be confirmed by a peak around δ = 7.4 ppm caused by Sn-φ bond using tetramethylsilane as a standard substance.
In gel permeation chromatography (GPC) analysis, 254 nm ultraviolet light was used for the detector.
The molecular weight distribution of polybutadiene that does not use component (e) cannot be measured. However, when, for example, diphenyltin dichloride is used as the component (e), the molecular weight distribution determined by ultraviolet rays and the molecular weight distribution determined by a differential refractometer are determined in correspondence with the presence of Sn-φ bonds.

The butadiene rubber obtained by the polymerization method is prepared into a rubber composition, further formed into a rubber, and provided on one or both of a tread and a sidewall of a pneumatic tire.

Butadiene rubber obtained by the polymerization method has a high cis 1,4
Although it is a polymer, it is necessary to use a cis
The 1,4 bond needs to be 70% or more, and preferably 90% or more. If the cis 1,4 bond is less than 70%, the desired low heat build-up cannot be achieved.

The molecular weight of the butadiene rubber obtained by the polymerization method can be varied over a wide range, but in order to achieve the effects of the present invention, the weight average molecular weight (w) must be
It must be in the range of 300,000 to 1.2 million. w is 30
If it is less than 10,000, all of the fracture resistance, abrasion resistance and low heat generation are reduced. If w exceeds 1.2 million, the tensile strength and the elongation at break decrease, so that when used in a pneumatic tire, the fracture resistance properties such as cut resistance, rib tear resistance, and chipping resistance decrease.

Further, the butadiene rubber obtained by the polymerization method can change the molecular weight distribution represented by the ratio w / n of the weight average molecular weight w and the number average molecular weight n over a wide range. W / n is 3 to play
It must be in the range of ~ 15. If w / n is less than 3, the breaking resistance such as cut property, rib tear property and chipping property is not sufficient. If w / n exceeds 15, the wear resistance decreases.

Butadiene rubber obtained by the polymerization method 10 to 100% by weight
And a rubber composition comprising 90 to 0% by weight of at least one diene rubber selected from the group consisting of natural rubber, isoprene rubber, styrene-butadiene rubber and butadiene rubber, and a rubber composition formed therefrom. Rubber
The effects of the present invention can be obtained by providing one or both of the tread and the sidewall. When the mixing amount of the butadiene rubber obtained by the polymerization method is less than 10% by weight, the abrasion resistance and the low heat build-up characteristic of the butadiene rubber are not sufficiently exhibited.

Further, carbon black can be added to the rubber composition, and the compounding amount of carbon black with respect to 100 parts by weight of the rubber component is such that the iodine adsorption amount is 80 to 150 g / kg and DBP is 100.
Preferably in the range of 30 to 80 parts by weight by using a carbon black having characteristics of ~180cm ² / 100g.

The mixture of the polybutadiene rubber and the diene rubber according to the present invention can be appropriately used for a rubber chafer, a carcass coating rubber, a base rubber, a bead filler rubber and the like in addition to a tread rubber and a sidewall rubber of a tire.

Examples Hereinafter, the present invention will be described specifically with reference to examples.

The microstructure defined in the present invention was measured by an infrared absorption spectrum method (Morello method). The weight average molecular weight w and the molecular weight distribution w / n were determined by measuring with a THF solvent using a 200 type GPC measuring device manufactured by Water.

The reaction between the living polymer and the component (e) immediately after polymerization with the lanthanum series rare earth metal catalyst is confirmed by GPC analysis and infrared analysis by changing the Mooney viscosity before and after the reaction or performing a model reaction with a number average molecular weight of several thousand. Was performed.

Mooney viscosity: 1 minute preheating, 4 minutes measurement, 100 ° C temperature
(Measured according to JIS K 6300). Polybutadiene rubbers of rubber samples Nos. 1 to 8 were obtained by the following polymerization method.

Rubber sample No. 1. In a nitrogen atmosphere, 2.5 kg of cyclohexane and 500 g of 1,3-butadiene were charged into a reactor equipped with a stirrer having an internal volume of 5, and then (a) 2-ethyl was prepared in the presence of 4.6 mmol of 1,3-butadiene. 0.93 mmol of neodymium hexanoate,
(B) triethylaluminum 27.7 mmol, (b) diisobutylaluminum hydride 10.2 mmol,
(C) 2.3 mmol of diethylaluminum chloride and (d) 1.85 mmol of acetylacetone were mixed,
A catalyst prepared by aging at 30 ° C. for 30 minutes was added, and a reaction was performed at 70 ° C. by an adiabatic reaction for 1.5 hours. The conversion of 1,3-butadiene was almost 100%. In order to measure Mooney viscosity, a part of the polymerization solution was withdrawn, coagulated and dried. Mooney viscosity was 49.

Next, after cooling the temperature of the polymerization solution to 60 ° C., 2.33 mmol of (e) diphenyltin dichloride was added. afterwards,
After stirring and leaving for 30 minutes, 3.0 g of 2,6-di-t-butyl-p-cresol was added, followed by steam coagulation and drying with a hot roll at 100 ° C. The microstructure of the poly-1,3-butadiene obtained in this reaction has a cis-1,4 bond content of 97.3%, a trans-1,4-linkage content of 1.3%, and a vinyl bond content of 1.4%.
%Met.

 The Mooney viscosity was 64.

Rubber Samples No.2 and No.3 Rubber sample No.2 used a commercially available polybutadiene (BR-01, manufactured by Nippon Synthetic Rubber Co., Ltd.) when diphenyltin dichloride of rubber sample No. 1 was not used.

Rubber sample Nos. 4 to 8 Rubber sample No. 4 has a molecular weight distribution (w /
If n) is narrowed, rubber sample No. 5 is larger than rubber sample No. 1 w is larger, rubber sample No. 6 is rubber sample No. 1 in which phenyltin trichloride is used instead of diphenyltin dichloride, and rubber sample No. 7 is rubber sample In the case where triphenyltin chloride was used instead of diphenyltin dichloride of No. 1, rubber sample No. 8 was the case where dibutyltin chloride was used instead of diphenyltin dichloride of rubber sample No. 1.

 Table 1 summarizes the rubber properties of the above samples.

Examples 1-4, Comparative Examples 1-4 Butadiene rubber samples No. 1-8 are as follows: Natural rubber 70 parts by weight Butadiene rubber 30 {ISAF carbon black 50} stearic acid 2 {amine-based antioxidant 1.5} lead zinc 4} sulfur A phenamide-based vulcanization accelerator was blended at a blending ratio of 1% of sulfur and 1.5% of sulfur, and a tread rubber was prepared by an ordinary method. These tread rubbers were applied to treads of a rib pattern tire of 1000R2014 ply of radial tires for trucks and buses, and respective test tires were manufactured by a usual tire manufacturing method. Table of test tire performance
It is shown in FIG.

Test Tests Each test was conducted on tires for tread rubber workability, tread rubber fracture resistance, and abrasion resistance, and is shown in Table-2.

The workability of the tread rubber was evaluated during the production of the tread rubber. Evaluation of the processability of the rubber, carbon dispersibility at the time of kneading the tread rubber, the properties of the unity of the rubber, the properties of the tread rubber at the time of extrusion, very good ◎, good ○, bad Was evaluated as △, and extremely poor ones were evaluated as ×.

The test for breaking resistance and abrasion resistance of tread rubber was conducted by mounting test tires on a test vehicle and testing on road surfaces including some unpaved roads.
I ran 10,000 km. The puncture resistance of the tread rubber was determined based on the presence or absence of a libty fault, a chipping fault, a cut fault over the entire area on the circumference of the tire tread, and the magnitude of the fault. The results were evaluated as very good 、, good 、, bad for △, and extremely bad for x. Further, the wear resistance of the tread rubber is compared by a value obtained by averaging the remaining grooves at eight places on the tire circumference, and the tire of Comparative Example 1 (BR01) is set to 100, and is indicated by an index using a wear index. Good wear resistance.

As an index of heat build-up, the rebound resilience (%) of a rubber sample sampled from a tire tread by a Dunlop resilience test was used. This measuring method conformed to BS903. The larger the rebound resilience (%), the less heat generation and the better.

As is clear from the test results shown in Table 2, Examples 1 to
No. 4 is comparative example 1 with respect to fracture resistance, exothermicity and especially abrasion resistance.
Better than ~ 4.

Example 5, Comparative Example 5 Next, it is shown that the ratio of the butadiene rubber according to the present invention in the rubber component must be 10 to 100% by weight.

For butadiene rubber, rubber sample No. 1 of Example 1 was used, and the mixing ratio of butadiene rubber and natural rubber was changed as shown in Table-3. Other formulations, tire production and test methods were the same as in Example 1. Table 3 shows the performance of the test tires.

As is clear from the test results shown in Table-3, Example 5 has improved wear resistance and low heat buildup over Comparative Example 5.

Examples 6 and 7, Comparative Examples 6 and 7 Next, the effects of the sidewalls will be described.

Butadiene sample No.1,2,3,8 is as follows. Natural rubber 50 parts by weight Butadiene rubber 50 〃 FEF carbon black 30 〃 GPF carbon black 20 〃 Aroma oil 15 亜 Zinc zinc 5 〃 Stearic acid 2 防止 Antioxidant 810NA 2 〃 Suntight E 2 〃vulcanization accelerator NBS 0.4 硫 vulcanization accelerator DM 0.3 硫黄 sulfur 1.5 〃 was compounded in a mixing ratio, and a side wall rubber was prepared by a usual method. These sidewall rubbers were applied to sidewalls of passenger car tires 175 / 70SR13, and respective test tires were manufactured by a usual tire manufacturing method. Table 4 shows the performance of the test tires.

Test (1) Crack growth resistance A specimen of 60 mm x 100 mm x 1.0 mm was placed with a 0.3 mm flaw at the center and subjected to elongational strain at a frequency of 300 cycles / min and a strain of 50%, and this grew to 20 mm. The time was evaluated until.

As the control, Comparative Example 7 was selected.

The larger the value, the better the crack growth resistance.

(2) Abrasion resistance A rubber sample sampled from a tire sidewall was evaluated according to ASTM D 2228 (pico method). The pico abrasion number was determined using the abrasion loss of Comparative Example 6 as a reference index of 100.
The larger the index, the better the wear resistance.

(3) Exothermicity A rubber sample sampled from the tire sidewall was evaluated by rebound resilience (%) in a Dunlop rebound resilience test. This measuring method conformed to BS903. The larger the rebound resilience (%), the less heat generation and the better.

(4) Weather resistance The presence / absence of ozone racks in the test tires after traveling up to 60,000 km was evaluated.

As is clear from the test results shown in Table 4, Examples 6 and 7
Has improved abrasion resistance and low heat buildup as compared with Comparative Examples 6 and 7.

[Effects of the Invention] According to the present invention, a pneumatic tire excellent in all of the fracture resistance, abrasion resistance and low heat generation required for tread rubber and sidewall rubber can be obtained.

Claims (1)

(57) [Claims] (1) (a) (a) a lanthanide series rare earth element compound and (b) a general formula AlR ¹ R ² R ³ (wherein R ¹ , R ² and R ³
Is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, except when all are hydrogen atoms), and if necessary, (c) Lewis acid and / or (d) Lewis acid In a polymer obtained by polymerizing 1,3-butadiene in an inert organic solvent in the presence of a catalyst containing a base, (e) a compound represented by the general formula R ′ _n MX _4-n (wherein
R 'is an alkyl or aryl group having 1 to 20 carbon atoms;
Is a tin atom or a germanium atom, X is a halogen atom, and n is an integer of 1 to 3).
Butadiene rubber having a weight average molecular weight of 300,000 to 1.2 million and a ratio (w / n) of weight average molecular weight (w) to number average molecular weight (n) of 3 to 15; (B) A rubber formed from a rubber composition containing 90 to 0% by weight of at least one diene rubber selected from the group consisting of natural rubber, isoprene rubber, styrene-butadiene rubber, and butadiene rubber as a rubber component. And / or a pneumatic tire provided on a sidewall.