JP2000256507A - Polybutadiene rubber and a method for producing the same. - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polybutazine rubber composite having a hexane-soluble portion having t-cp> 4ML, and a method for producing the same. SOLUTION: A polybutadiene rubber comprising (A) 10 to 25% by weight of a specific 1,2-polybutadiene component and (B) 90 to 75% by weight of a specific high cis polybutadiene component, and (a) a periodic table Group 3 metal compounds,
Butadiene is polymerized using a catalyst obtained by aging (b) alkylaluminum hydride, (c) butadiene, and (d) alkylaluminum chloride, and syndiotactic-1 in the presence of the obtained polymerization solution. , 2-butadiene is further polymerized in the presence of a polymerization catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polybutadiene rubber comprising a specific n-hexane-insoluble component and a specific n-hexane-soluble component, a polybutadiene rubber using a polymerization catalyst comprising a compound of a Group 3 metal of the periodic table, and The present invention relates to a production method in which the polymerization is performed in a non-aromatic solvent.

[0002]

2. Description of the Related Art It is known that a polymer having various microstructures can be obtained from polybutadiene by a polymerization catalyst. Polybutadiene using a cobalt compound or a nickel compound and an organoaluminum compound is generally called high cis BR because of its microstructure characteristics (95% or more in cis content). Produced and used.
In addition, taking advantage of the features of these high-cis BRs, the high-cis BRs are included in the high-cis BR as 1
A composite rubber (VCR) in which -2 syndiotactic polybutadiene (hereinafter abbreviated as SPB) is dispersed is known.

Japanese Patent Publication No. 49-17666 discloses a method for producing a SPB-containing high cis BR composite using a cobalt catalyst. Japanese Patent Publication No. 63-1324 discloses a method for producing a SPB-containing high cis BR composite using a nickel catalyst.

In addition, Japanese Patent Publication No. 2-62123 and Japanese Patent Publication No. 4
No.-48815 discloses a similar BR composition and a method for producing the same.

Further, Japanese Patent Application Laid-Open No. 3-45609 discloses that
It is disclosed that the high cis BR of the composite is a butadiene rubber having the property of t-cp> 3ML-30, and that the rebound resilience is improved. However, what is specifically described is that t-cp / 3ML is about 2 to 3. Further, as a polymerization catalyst for the high cis BR, there is a description of a lanthanum series rare earth element-based catalyst (eg, triethylaluminum / neodymium organic acid / Lewis acid-based catalyst), but no specific catalyst is described.

[0006] Japanese Patent Application Laid-Open No. 5-194658 discloses that the high cis BR of the complex is 3ML-30 <t-cp <3ML.
It is a butadiene rubber having a characteristic of +30, and discloses that the balance of various characteristics is excellent while maintaining the advantages of polybutadiene. However, the t-cp of the rubber according to the example of the above publication is at most about 100 to 200, and t-cp / ML is 2 to 4.

[0007] The viscosity of toluene solution (t-cp) and the Mooney viscosity (M
L) (t-cp / ML). t-cp indicates the degree of entanglement of molecules in a concentrated solution. For high cis polybutadiene having a similar molecular weight distribution, t-cp indicates that the molecular weight is the same (that is, the ML is the same).
It is an index of the branching degree (the larger the t-cp,
The degree of branching is small). Further, t-cp / ML is used as an index when comparing the degree of branching of high cis polybutadiene having different MLs (the greater the t-cp / ML, the smaller the degree of branching).

When the composite is used for various members of a tire or other uses, characteristics that cannot be obtained by conventional methods may be required, and higher t-cp or higher t-cp may be required.
-Cp / ML may be required.

Further, the hexane-insoluble portion of the above complex is 2
It is described that it has an endothermic peak of a differential calorimeter (DSC) around 00 ° C.

It is desired that a non-aromatic solvent such as an aliphatic hydrocarbon solvent be used in the polymerization reaction for producing the above-mentioned complex.

As a method for obtaining polybutadiene having a high cis-1,4 structure, a polymerization catalyst using a metal compound of Group 3 of the periodic table in addition to the above catalyst system is known.

For example, Japanese Patent Publication No. 47-14729 discloses a polymerization catalyst using a metal compound of Group 3 of the Periodic Table, a compound of a Group 3 metal of the Periodic Table such as cerium octanoate and diisobutylaluminum hydride. A catalyst system comprising an alkylaluminum hydride such as an alkylaluminum hydride or an alkylaluminum halide such as a trialkylaluminum and ethylaluminum dichloride has been shown.In particular, it has been shown that the catalyst activity is increased by aging the catalyst in the presence of butadiene. I have.

JP-B-63-64444 discloses a catalyst system comprising a carboxylate of a rare earth element, an organic aluminum and a Lewis acid. JP-B-4-2601 discloses a catalyst system of a carboxylate of a rare earth element, an organic aluminum and an organic halogen. Catalyst system comprising a derivative, JP-A-7-26
No. 8013 discloses a catalyst system comprising a rare earth salt, a metal compound of Groups I to III of the periodic table and an organometallic derivative of trivalent boron. Japanese Patent Publication No. 3-22887 discloses a neodymium compound, an organic aluminum compound and A catalyst system comprising water is disclosed.

[0014]

SUMMARY OF THE INVENTION A polybutazine rubber composite having a novel property, that is, a hexane-soluble part having t-cp> 4 ML, a method for producing the same, that is, a polymerization catalyst based on a Group 3 metal compound of the related periodic table. To produce high cis polybutadiene with high activity, followed by 1,2-
Cis-1,2 characterized by producing polybutazine
To provide a method for producing a polybutadiene complex and a method for carrying out the polymerization in a non-aromatic solvent.

[0015]

According to the present invention, there are provided (A) a boiling n-hexane-insoluble component containing 10-25% by weight of 1,2-polybutadiene having a reduced viscosity of 0.5 to 4, and (B) Toluene solution viscosity (t-cp) and 100 ° C.
And the Mooney viscosity (ML) at t-cp> 4ML
A polybutadiene rubber comprising high cis polybutadiene as a main component and having a boiling n-hexane soluble content of 90 to 75% by weight.

The present invention further provides a differential calorimeter (DS)
The fact that the endothermic curve C) has a double peak in the range of 170 to 210 ° C. relates to the above-mentioned polybutadiene rubber.

Further, the present invention uses a catalyst obtained by aging (a) a compound of a metal belonging to Group 3 of the periodic table, (b) an alkylhydroaluminum compound, (c) butadiene, and (d) an alkylaluminum chloride. And polymerizing butadiene, and further polymerizing butadiene in the presence of the resulting polymerization solution in the presence of a syndiotactic-1,2-polymerization catalyst.

The present invention also relates to the above method for producing a polybutadiene rubber, wherein the polymerization is carried out in a non-aromatic solvent.

The polybutadiene rubber of the present invention has a boiling n-
It consists of a hexane insoluble matter and a boiling n-hexane soluble matter.

The boiling n-hexane insolubles are those containing, as a main component, syndiotactic-1,2-polybutadiene and / or polybutadiene having syndiotactic-1,2-polybutadiene as a main structure. On the other hand, the components soluble in boiling n-hexane are those containing high cis-1,4-polybutadiene as a main component.

The proportion of the boiling n-hexane insoluble component is 10 to
It needs to be 25% by weight. If the proportion of the boiling n-hexane insoluble matter is less than 10% by weight, there arises a problem that the hardness, elastic modulus, and breaking strength of the polybutadiene rubber decrease. On the other hand, when the content is more than 25% by weight, the blend ML of the polybutadiene rubber becomes too high, resulting in difficulty in workability. Here, the “compound” refers to a compound obtained by mixing carbon black, a process oil, a vulcanizing agent, and the like with a polybutadiene rubber or a rubber composition obtained by mixing another polyene rubber with the polybutadiene rubber.

The boiling n-hexane insoluble matter requires that the reduced viscosity calculated from the viscosity measured at 130 ° C. in tetralin be in the range of 0.5 to 4. If the reduced viscosity is less than 0.5, the boiling n-hexane insolubles do not disperse in a fibrous form in the boiling n-hexane solubles.
There is a problem that the hardness, elasticity, and bending resistance of the obtained polybutadiene rubber are reduced. On the other hand, if the reduced viscosity exceeds 4, the boiling n-hexane insolubles will form agglomerates in the boiling n-hexane solubles, which tends to cause poor dispersion. The problem that the property falls is arisen.

The boiling n-hexane soluble matter preferably has a weight average molecular weight in the range of 300,000 to 1,000,000. or,
Ratio M between weight average molecular weight (Mw) and number average molecular weight (Mn)
w / Mn is preferably from 2 to 5. When the weight average molecular weight is smaller than the above range, there is a problem that the durability of the obtained polybutadiene rubber is deteriorated. on the other hand,
If the weight average molecular weight is larger than the above range, the Mooney viscosity of the composition becomes too high, and there is a problem that processing becomes difficult. In addition, the fluidity of the compounded rubber also deteriorates.

Further, the boiling n-hexane-soluble matter has its own toluene solution viscosity (t-cp) and Mooney viscosity (M
L) must satisfy the relationship of t-cp> 4ML. The toluene solution viscosity indicates the degree of entanglement of molecules of the boiling n-hexane soluble component in a concentrated solution, and for rubbers having the same molecular weight distribution,
The same molecular weight (ie, the same Mooney viscosity) is a measure of the degree of polymer chain branching. That is, in the case of the same Mooney viscosity, a lower viscosity of the toluene solution indicates a higher degree of branching, and a higher viscosity of the toluene solution indicates a lower degree of branching. When the above relationship is satisfied, the balance of properties such as high hardness, high modulus, tear resistance, and abrasion resistance is improved.

The hexane-insoluble component (A) is
Preferably, the DSC endothermic curve has a double peak in the range of 170 to 210 ° C. In general, vulcanization of automobile tires and the like is carried out at around 175 ° C, and the hexane-insoluble (A) component is added together with the conventional melting point of around 200 ° C.
By having another endothermic peak around 75 ° C,
Co-vulcanization with other rubbers easily occurs, and there is an effect that a decrease in tire strength is small.

Hereinafter, the method for producing the polybutadiene rubber of the present invention will be described. The production method includes, for example, a two-stage polymerization method.

The two-stage polymerization method means that 1,3-butadiene is first cis-1,4-polymerized to form high cis-1,4-polybutadiene, and then the syndiotactic-1,4-polybutadiene is added to the polymerization system.
(2) The polymerization catalyst was charged, and the remaining 1,3-butadiene was converted into 1,
It is to polymerize two. As the 1,4-polymerization catalyst, a catalyst obtained by aging (a) a compound of a metal belonging to Group 3 of the periodic table, (b) an alkylaluminum hydride compound, (c) butadiene, and (d) an alkylaluminum chloride is preferable. .

The metal constituting the compound of the Group 3 metal of the periodic table, which is the component (a) of the catalyst system, is an atom belonging to Group 3 of the periodic table, and examples thereof include lanthanum series elements and actinium series elements. . Preferably, a rare earth element is used. Specifically, it is neodymium, praseodymium, cerium, lanthanum, gadolinium or a mixture thereof. Particularly preferably, neodymium is used.

Examples of the compound of the Group 3 metal of the Periodic Table include carboxylate, alkoxide, β-diketone complex, phosphate and phosphite of the Group 3 metal of the Periodic Table. Acid salts are preferred, especially carboxylate salts.

The carboxylate of a metal belonging to Group 3 of the periodic table is represented by the general formula (RCO ₂ ) ₃ M, wherein M is a metal belonging to Group 3 of the periodic table, and R is a hydrocarbon group having 1 to 20 carbon atoms. ).

R is a saturated or unsaturated alkyl group and is linear, branched or cyclic, and the carboxyl group CO ₂ is bonded to a primary, secondary or tertiary carbon atom. Specifically, octanoic acid, 2-ethyl-hexanoic acid, oleic acid, stearic acid, benzoic acid, naphthenic acid and vasatic acid (trade names of shell chemistry, in which a carboxyl group is bonded to a tertiary carbon atom) Carboxylic acid). Among them, 2-ethyl-hexanoic acid and versatic acid are preferred.

The alkoxide of the Group 3 metal of the periodic table is a compound represented by the general formula (RO) ₃ M (wherein M and R are the same as described above). Examples of the alkoxy group represented by RO include 2-ethyl-hexylalkoxy,
Oleylalkoxy, stearylalkoxy, phenoxy and benzylalkoxy groups are mentioned. Above all,
2-ethyl-hexylalkoxy and benzylalkoxy groups are preferred.

Examples of the β-diketone complex of a Group 3 metal of the periodic table include acetylacetone, benzoylacetone, propionitrileacetone, valerylacetone, and ethylacetylacetone complexes of the Group 3 metals of the periodic table. Among them, acetylacetone and an ethylacetylacetone complex are preferred.

Examples of the phosphate or phosphite of the Group 3 metal of the periodic table include bis (2-ethylhexyl) phosphate, bis (1-methylheptyl) phosphate, and bis (phosphate) of the Group 3 metals of the periodic table. (P-nonylphenyl), bis (polyethyleneglycol-p-nonylphenyl) phosphate, (1-methylheptyl) phosphate (2-ethylhexyl), (2-ethylhexyl) phosphate (p-nonylphenyl), 2
Mono-2-ethylhexyl-ethylhexylphosphonate, mono-2-nonylphenyl 2-ethylhexylphosphonate, bis (2-ethylhexyl) phosphinic acid,
Bis (1-methylheptyl) phosphinic acid, bis (p-
Nonylphenyl) phosphinic acid, (1-methylheptyl) (2-ethylhexyl) phosphinic acid, and salts such as (2-ethylhexyl) (p-nonylphenyl) phosphinic acid. Of these, salts such as bis (2-ethylhexyl) phosphate, bis (1-methylheptyl) phosphate, mono-2-ethylhexyl 2-ethylhexylphosphonate, and bis (2-ethylhexyl) phosphinic acid are preferred.

Of the above examples, particularly preferred are neodymium phosphate and neodymium carboxylate, and further, carboxylate such as neodymium 2-ethyl-hexane salt and neodymium vasatic salt. Most preferred.

Further, as the alkyl aluminum hydride compound (b) of the above catalyst system, diethyl aluminum hydride, dipropyl aluminum hydride, di-n-butylethyl aluminum hydride,
Diisobutylaluminum hydride, diphenylaluminum hydride and the like can be mentioned.

The (d) alkylaluminum chloride of the above catalyst system includes dialkylaluminum halides such as dialkylaluminum chloride and dialkylaluminum bromide, alkylaluminum sesquichlorides such as alkylaluminum sesquichloride and alkylaluminum sesquibromide, and alkylaluminum dichloride. And alkyl aluminum dihalides such as alkyl aluminum dibromide. Specific compounds include diethylaluminum monochloride, diethylaluminum monobromide, dibutylaluminum monochloride, ethylaluminum sesquichloride, ethylaluminum dichloride, dicyclohexylaluminum monochloride, diphenylaluminum monochloride and the like.

The components of the above-mentioned catalyst are preferably in the following proportions. (B) :( a) = 1: 1 to 100: 1 (molar ratio) (c) :( a) = 0.5: 1 to 200: 1 (molar ratio) (d) :( a) = 1: 1 to 10: 1 (molar ratio)

It is preferable that the above-mentioned catalyst system is aged and used. The aging time is preferably from 1 minute to 150 minutes. The aging temperature is preferably from -10C to 30C.

As the polymerization solvent, pentane, hexane,
Non-aromatic solvents such as aliphatic hydrocarbons such as heptane and cyclohexane, and cycloaliphatic hydrocarbons are preferred.

As the syndiotactic-1,2-polymerization catalyst, known catalysts can be used. For example, a soluble cobalt-organoaluminum compound-carbon disulfide catalyst (Japanese Patent Publication No. 47-19892), or a catalyst obtained by further adding acrylonitrile to this catalyst system (Japanese Patent Publication No. 47-1989)
No. 3).

Among them, a catalyst obtained from (e) carbon disulfide, (f) an organoaluminum compound, and (g) a cobalt compound is preferable. (F) Examples of the organoaluminum compound include trialkylaluminum, dialkylaluminum chloride, dialkylaluminum bromide, alkylaluminum sesquichloride, and alkylaluminum sesquibromide. Among them, trialkylaluminum is preferable, and specific examples include trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, and trioctylaluminum.

(G) Examples of the cobalt compound include cobalt salts such as cobalt chloride, cobalt bromide, cobalt nitrate, cobalt octylate, cobalt naphthenate, cobalt acetate, and cobalt malonate; and bisacetylacetonate and trisacetyl of cobalt. Triarylphosphine complexes and trialkylphosphine complexes of acetonate, acetoacetate ethyl ester cobalt, cobalt halide,
Alternatively, an organic base complex such as a pyridine complex or a picoline complex, or an ethyl alcohol complex may be used.

Further, in addition to the above catalyst, alcohol,
Addition of aldehydes, ketones, esters, nitriles, sulfoxides, amides, phosphates and the like can give syndiotactic-1,2-polybutadiene having a low melting point.

As the polymerization solvent, pentane, hexane,
Non-aromatic solvents such as aliphatic hydrocarbons such as heptane and cyclohexane, and cycloaliphatic hydrocarbons are preferred. The polymerization solvent and the like can be appropriately set according to a known method.

The polybutadiene rubber of the present invention can also be produced by a blending method. In the blending method, high cis 1,4-polybutadiene and syndiotactic 1,2-polybutadiene are separately polymerized in advance, and the respective polymerization solutions are blended. other than this,
A method of blending a solid syndiotactic 1,2-polybutadiene with a polymerization solution of high cis 1,4-polybutadiene is also possible.

The polybutadiene rubber of the present invention is a composition comprising at least one rubber selected from the group consisting of high cis polybutadiene rubber, low cis polybutadiene rubber, styrene-butadiene rubber, isoprene rubber, butyl rubber, and natural rubber. As a base tread or sidewall of a tire or a bead filler. However, this composition desirably contains at least 20% by weight of the polybutadiene rubber of the present invention.

[0048]

EXAMPLES In the following examples and comparative examples, the following items were measured for butadiene rubber as follows.

Reduced viscosity of n-hexane insoluble matter: 25 g of polybutadiene rubber was refluxed in 1000 ml of boiling n-hexane to separate into boiling n-hexane insoluble matter and soluble matter.
0.2 g of the obtained boiling n-hexane insoluble matter was dissolved in 100 ml of tetralin and measured at 130 ° C. with an Ubbelohde viscometer. The endothermic curve by DSC was measured using.

Measurement of weight average molecular weight of n-hexane soluble component: 25 g of polybutadiene rubber was boiled with 10 parts of n-hexane.
The mixture was refluxed in 00 ml, and the boiling n-hexane insoluble matter was filtered off.
The n-hexane solution was recovered. The n-hexane was removed from the obtained n-hexane solution, and the n-hexane soluble matter was recovered. The recovered n-hexane soluble matter was dissolved in tetrahydrofuran, and Mw was calculated from the molecular weight in terms of polystyrene using GPC. The measurement conditions are as follows. Dress
Place: HLC-802A type (manufactured by Toyo Soda Co., Ltd.) Column: GMH6000, two parallel eluent: tetrahydrofuran Eluent flow rate: 1.0 ml / min Measurement temperature: column tank 40 ° C. detector 40 ℃ Sample concentration:
0.025g / 100ml Sample injection volume: 0.5ml

Microstructure of n-hexane soluble component: The boiling n-hexane soluble component obtained by the above method was analyzed by infrared absorption spectrum method (Morello method) to obtain cis-1,4.
The proportion of the structure was quantified.

Viscosity of n-hexane-soluble component in toluene solution (T-cp): The boiling n-hexane-soluble component obtained by the above method was dissolved in toluene so as to have a concentration of 5% by weight. The viscometer was measured at 25 ° C.

The n-hexane solubles and Mooney viscosity of the blend were measured according to the measuring method specified in JIS-K-6300.

Example 1 (Aging of Catalyst) 3.13 mmol of diisobutylaluminum hydride (2 ml of n-hexane solution), 3.57 mmol of butadiene (cyclohexane solution) and Nd
0.13 mmol of V ₃ (neodymium versatate) (cyclohexane solution) was mixed and aged at 20 ° C. for 10 minutes. Further, 0.36 of diethyl aluminum chloride
mmol (n-hexane solution) was added, and the mixture was aged for 20 minutes. (High cis polymerization) 1,3-butadiene 28.8 was placed in a 2-liter autoclave in which the inside was replaced with nitrogen gas.
% by weight and 71.2% by weight of cyclohexane
Solution B was charged. Add all of the above catalyst aging solution,
Polymerization was performed at 60 ° C. for 60 minutes. (Production of VCR) Carbon disulfide 15 was added to the above cis polymerization solution.
mg / L, 0.4 mg / L of triethylaluminum, and 30 mg / L of cobalt octoate, and
Stirring was performed at 30 ° C. for 30 minutes to polymerize the remaining 1,3-butadiene into syndiotactic 1,2. After terminating the polymerization reaction, the polymerization solution was treated according to a conventional method to recover polybutadiene rubber. The resulting polybutadiene rubber had a yield of 115 g and a Mooney viscosity of 52 (ML1 + 4, 1
00 ° C)

The content of the boiling n-hexane insoluble component was 12% by weight, and the content of the boiling n-hexane soluble component was 88% by weight. The boiling n-hexane insoluble matter has a reduced viscosity of 1.2, and its endothermic curve measured by DSC shows 176 ° C and 191.6 ° C.
(See FIG. 1). The boiling n-hexane solubles have a Mooney viscosity of 35 (ML1 + 4, 100
C), a toluene solution viscosity of 80 and a weight average molecular weight of 40
And the ratio of the cis-1,4 structure was 98%.

(Comparative Examples 1-2) (Examples 1-3) (Effect of Catalyst Aging Time) Except that the first stage cis polymerization was carried out under the conditions shown in Table 1, the examples were carried out in the same manner. Was. The results of the high cis polymerized portion are shown in Tables 1 and 2.

(Examples 5 to 8) (Effect of Catalyst Aging Time) The same procedures as in Examples were carried out except that the first stage high cis polymerization was carried out under the conditions shown in Table 3. Tables 3 and 4 show the results of the high cis polymerization portion.

(Examples 9 to 10) (Effect of high cis polymerization time) The same procedure as in Examples was carried out except that the first stage of high cis polymerization was carried out under the conditions shown in Table 5. Tables 5 and 6 show the results of the high cis polymerization portion.

(Examples 11 to 13) (Effect of high cis polymerization temperature) The same procedure as in Examples was carried out except that the first stage of high cis polymerization was carried out under the conditions shown in Table 7. Tables 7 and 8 show the results of the high cis polymerization portion.

(Examples 14 to 17) (Effect of molar ratio of (b) / (a) in high cis polymerization) Except that the first stage high cis polymerization was carried out under the conditions shown in Table 9, the following examples were used. Performed similarly. Tables 9 and 10 show the results of the high cis polymerization portion.

(Examples 18 to 20) (Effect of molar ratio of (d) / (a) in high cis polymerization) Except that the first stage high cis polymerization was carried out under the conditions shown in Table 11, the following examples were used. Performed similarly. Tables 11 and 12 show the results of the high cis polymerization portion.

(Examples 21 to 23) (Effect of Type of Component (a) in High-cis Polymerization) Except that the first stage of high-cis polymerization was performed under the conditions shown in Table 13, the examples were performed in the same manner. . Tables 13 and 14 show the results of the high cis polymerization portion.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

[0066]

[Table 4]

[0067]

[Table 5]

[0068]

[Table 6]

[0069]

[Table 7]

[0070]

[Table 8]

[0071]

[Table 9]

[0072]

[Table 10]

[0073]

[Table 11]

[0074]

[Table 12]

[0075]

[Table 13]

[0076]

[Table 14]

[Brief description of the drawings]

FIG. 1 is a DSC chart of the component (A) of one embodiment of the present invention.
It is.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4J002 AC031 AC032 AC042 4J011 HA03 HB22 PA04 PA76 PC01 4J015 DA05 DA14 4J100 AS02P CA01 CA12 CA14 DA09 DA24 DA40 FA08 FA30 FA34 JA29

Claims (4)

[Claims] (A) A boiling n-hexane insoluble component containing 1,2-polybutadiene having a reduced viscosity of 0.5 to 4 as a main component.
··· 10 to 25% by weight, and (B) toluene solution viscosity (t-cp) and Mooney viscosity at 100 ° C (ML)
Is a boiling n-hexane soluble component containing high cis polybutadiene as a main component satisfying a relationship of t-cp> 4ML.
.. Polybutadiene rubber consisting of 90 to 75% by weight. 2. The component (A) further comprises a differential calorimeter (D
The polybutadiene rubber according to claim 1, wherein the endothermic curve of SC) has a double peak in the range of 170 to 210 ° C. (A) a compound of a metal belonging to Group 3 of the periodic table;
(B) an alkyl aluminum hydride compound,
(B) Polymerization of butadiene using a catalyst obtained by aging (c) butadiene and (d) alkylaluminum chloride, and the presence of a syndiotactic-1,2-polymerization catalyst in the presence of the resulting polymerization solution 3. The method for producing a polybutadiene rubber according to claim 1, wherein butadiene is further polymerized. 4. The method for producing a polybutadiene rubber according to claim 3, wherein the polymerization is carried out in a non-aromatic solvent.