JPH06136033A - Production of butadiene-based polymer having high vinyl bond - Google Patents

Abstract

PURPOSE:To produce a butadiene-based polymer capable of lowering a glass transition temperature without damaging reduction in a melting point by polymerizing a conjugated diene in a polymer hydrocarbon solvent in high activity to give a having high vinyl bond content. CONSTITUTION:A conjugated diene containing at least >=50mol% 1,3-butadiene is polymerized in an inert organic solvent by using a catalyst containing (A) an organic acid salt of cobalt, (B) a mixed ligand composed of an alicyclic hydrocarbon phosphine and an aromatic hydrocarbon phosphine and (C) an organoaluminum compound containing aluminoxane in an inert organic solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a butadiene-based polymer having a high vinyl bond, and more specifically, it has a high vinyl bond content and has a low glass transition temperature (Tg) without impairing the lowering of the melting point. The present invention relates to a method for producing a butadiene-based polymer which is excellent in low temperature characteristics and can be made into a polymer.

[0002]

2. Description of the Related Art 1,2-Polybutadiene, which is controlled to have an appropriate degree of crystallinity, has a structure consisting of a highly crystalline region and an amorphous portion, and therefore, not only functions as a thermoplastic elastomer, but also has a molecular weight. Since it has a carbon-carbon double bond rich in chemical reactivity, it also functions as a conventional vulcanized rubber or a thermosetting resin having an increased crosslink density. In addition, this 1,
Since 2-polybutadiene has excellent processability, it has been developed as a modifier for other resins and thermoplastic elastomers, and a polymer material for medical use.

Conventionally, these crystallinity-controlled 1,
2-Polybutadiene is a catalyst composed of a phosphine complex of cobalt salt, trialkylaluminum and water (Japanese Patent Publication No.
No. 4-32425), a catalyst containing a cobalt compound, a trialkylaluminum and water, and a triphenylphosphine derivative (Japanese Patent Publication No. 61-27402).
It has been obtained by. In these catalyst systems, halogenated hydrocarbon solvents typified by methylene chloride show high polymerization activity, but general-purpose hydrocarbon solvents have a problem that the polymerization activity decreases. Further, the control range of the molecular weight and melting point, which are the molecular characteristics of the obtained polymer, is relatively narrow,
It has not been possible to produce a polymer whose molecular properties are controlled over a wide range. For example, the former is difficult to produce in a high molecular weight region, and the latter requires the use of a special ligand for producing a polymer having high crystallinity (high melting point). Therefore, even if the polymerization temperature is lowered to carry out the polymerization,
The polymerization rate slows down, productivity decreases, and the upper limit of the crystallinity (melting point) is naturally limited.

In view of the above problems, the applicant of the present invention previously polymerized with a high activity even in a hydrocarbon solvent by using a specific catalyst system, and the obtained polymer had a high vinyl bond content and crystallized. The invention provides a method for producing a butadiene-based polymer, which has high properties and is capable of controlling the crystallinity (melting point) of the polymer (Japanese Patent Application No. 4-31312). However, in the conventional production method of crystalline 1,2-polybutadiene and the above-mentioned production method by the applicant, the glass transition temperature which governs the low temperature characteristics of the obtained polymer depends on the melting point defined by the polymerization catalyst. The relationship was decided. That is, the glass transition temperature (Tg)
It means that the ratio of (K) / melting point (Tm) (K) is constant. In other words, as the melting point is raised and the heat resistance is imparted, the glass transition temperature also rises, so that there is a problem that the low temperature characteristics are sacrificed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. Polymerization with high activity in a hydrocarbon solvent results in a polymer having a high vinyl bond content and a melting point. It is an object of the present invention to provide a method for producing a butadiene-based polymer capable of achieving a low glass transition temperature without impairing the decrease in

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, a conjugated diene containing 1,3-butadiene in an amount of at least 50 mol% or more is used, (A) an organic acid salt of cobalt, (B) an alicyclic hydrocarbon phosphine and an aroma. Polymerization in an inert organic solvent using a mixed ligand composed of a group hydrocarbon phosphine (hereinafter sometimes referred to as “(B) phosphine compound”) and (C) an organoaluminum-containing aluminoxane. And a method for producing a butadiene-based polymer having a high vinyl bond.

The conjugated dienes other than 1,3-butadiene used in the present invention include 4-alkyl-substituted-1,3-butadiene.
Examples thereof include butadiene and 2-alkyl-substituted-1,3-butadiene. Of these, 4-alkyl-substituted-1,3
-As butadiene, 1,3-pentadiene, 1,3
-Hexadiene, 1,3-heptadiene, 1,3-octadiene, 1,3-nonadiene, 1,3-decadiene and the like.

Typical examples of 2-alkyl-substituted-1,3-butadiene include 2-methyl-1,3-butadiene (isoprene), 2-ethyl-1,3-butadiene,
2-propyl-1,3-butadiene, 2-isopropyl-1,3-butadiene, 2-butyl-1,3-butadiene, 2-isobutyl-1,3-butadiene, 2-amyl-1,3-butadiene, 2-isoamyl-1,3-butadiene, 2-hexyl-1,3-butadiene, 2-cyclohexyl-1,3-butadiene, 2-isohexyl-
1,3-butadiene, 2-heptyl-1,3-butadiene, 2-isoheptyl-1,3-butadiene, 2-octyl-1,3-butadiene, 2-isooctyl-1,3
-Butadiene and the like. Among these conjugated dienes, isoprene and 1,3-pentadiene are preferable as the conjugated diene used as a mixture with 1,3-butadiene. The content of 1,3-butadiene in the monomer component used for the polymerization is 50 mol% or more, preferably 70 mol% or more, more preferably 80 mol% or more, and if less than 50 mol%, the butadiene obtained is less than 50 mol%. It is not preferable because the polymer does not have a melting point and becomes amorphous.

Next, the organic acid salt of cobalt (A) used in the catalyst of the present invention is preferably an organic acid salt of cobalt having 4 or more carbon atoms from the viewpoint of solubility in an organic solvent. The organic acid salt of cobalt (A) is an octyl acid salt such as butyric acid salt, hexyl acid salt, heptyl acid salt, 2-ethylhexyl acid or decanoic acid salt, or higher stearic acid, oleic acid, erucic acid or the like. Alkyl such as fatty acid salt, benzoate, tolylate, xylylate and ethylbenzoic acid,
Examples thereof include aralkyl, allyl-substituted benzoate, naphthoate, alkyl, aralkyl- or allyl-substituted naphthoate. Of these, so-called octylates of 2-ethylhexyl acid, stearates and benzoates are preferable because of their excellent solubility in organic solvents.

Among the catalysts of the present invention, the (B) phosphine compound is used to activate the polymerization catalyst, impart a vinyl bond structure and crystallinity and control the crystallinity, the relationship between the melting point and the glass transition temperature, in other words, For example, it is an essential component for controlling the distribution of crystallinity, and is a combination of an alicyclic hydrocarbon phosphine and an aromatic hydrocarbon phosphine among the organic phosphorus compounds represented by the general formula (I), or the organic phosphorus compound. It is the compound itself.

[0011]

[Chemical 1]

The carbon number of R ¹ , R ² and R ³ is not particularly limited, but is preferably 1-6. Among the (B) phosphine compounds, as the alicyclic hydrocarbon phosphine,
Tricyclopentylphosphine, tri (methylcyclopentyl) phosphine, tricyclohexylphosphine,
Examples thereof include tri (methylcyclohexyl) phosphine and tri (dimethylcyclohexyl) phosphine, with cyclohexylphosphine being preferred.

Among the (B) phosphine compounds, aromatic hydrocarbon phosphines include tri (3-methylphenyl) phosphine, tri (3-ethylphenyl) phosphine, tri (4-methylphenyl) phosphine, tri (3-methylphenyl) phosphine. 3,5-dimethylphenyl) phosphine, tri (3,3
4-dimethylphenyl) phosphine, tri (3-isopropylphenyl) phosphine, tri (3-t-butylphenyl) phosphine, tri (3,5-diethylphenyl) phosphine, tri (3-methyl-5-ethylphenyl) phosphine ), Tri (3-phenylphenyl) phosphine, tri (3,4,5-trimethylphenyl) phosphine, tri (4-methoxy-3,5-dimethylphenyl) phosphine, tri (4-ethoxy-3,5-diethyl) Phenyl) phosphine, tri (4-butoxy-3,5)
-Dibutylphenyl) phosphine, tri (4-methoxyphenyl) phosphine, tri (3-methoxyphenylphosphine), tribenzylphosphine, tri (4-methylphenylphosphine), 1,2-diphenylphosphinoethane, 1,3- Diphenylphosphinopropane,
1,4-diphenylphosphinobutane, tri (4-ethylphenylphosphine), and the like. The aromatic hydrocarbon phosphine is preferably triphenylphosphine, tri (3-methylphenyl) phosphine, tri (4-methoxy-3,5-dimethylphenyl) phosphine, tri (4-methoxyphenyl) phosphine and the like.

Further, among the (B) phosphine compounds,
Examples of the compound in which the alicyclic hydrocarbon phosphine and the aromatic hydrocarbon phosphine are chemically bound in advance include dicyclohexylphenylphosphine, dicyclohexylbenzylphosphine, cyclohexyldiphenylphosphine, neomenthyldiphenylphosphine and the like.

The phosphine compound (B) is a mixed ligand composed of the (B-1) alicyclic hydrocarbon phosphine and the (B-2) aromatic hydrocarbon phosphine as described above,
The ratio of both is (B-1) / (B-2) (molar ratio) = 3
/ 97 to 97/3, preferably 5/95 to 95/5. If this molar ratio is less than 3/97, the effect of lowering the glass transition temperature is small, while if it exceeds 97/3, it becomes difficult to prepare the crystalline polymer, which is not preferable.

Further, among the catalysts of the present invention, examples of the aluminoxane (C) constituting the organoaluminum include, for example, the general formula (II) or the general formula (III).

[0017]

[Chemical 2]

[0018]

[Chemical 3]

An organic aluminum compound represented by the formula (wherein R'is a hydrocarbon group and m is an integer of 2 or more) can be given. In the aluminoxane represented by the general formula (II) or (III), R'is a hydrocarbon group such as methyl group, ethyl group, propyl group and butyl group, preferably methyl group and ethyl group. , And particularly preferably a methyl group. In addition, m is an integer of 2 or more, preferably 5 or more, and more preferably 10 to 100.
Specific examples of this aluminoxane include methylaluminoxane, ethylaluminoxane, propylaluminoxane, butylaluminoxane, and the like.

At this time, as (C) organoaluminum,
An aluminum compound other than the aluminoxane may be used in combination. Examples of other aluminum compounds include alkylaluminums, alkylaluminum halide compounds, and alkylaluminum alkoxides. Among these, examples of the alkyl aluminum include trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, trihexyl aluminum and the like.

The alkylaluminum halide compound has the general formula AlR ⁴ _p X _3-p (wherein R ⁴ is an alkyl group, X is a halogen atom, p is 0, 1, 1.5 or 2).
Is shown). Here, the alkyl group has 1 carbon atom.
Linear or branched alkyl groups having 8 to 8, for example, methyl group, ethyl group, propyl group, n-butyl group, isobutyl group, hexyl group, octyl group and the like.
Further, examples of the halogen atom X include a fluorine atom, a chlorine atom and an iodine atom, and a chlorine atom is particularly preferable.

Specific examples of the alkylaluminum halide compound include diethyl aluminum fluoride, diethyl aluminum chloride, diethyl aluminum bromide, diethyl aluminum iodide, diisobutyl aluminum fluoride, diisobutyl aluminum chloride, diisobutyl aluminum bromide, diisobutyl aluminum iodide. , Dihexyl aluminum fluoride, dihexyl aluminum chloride, dihexyl aluminum bromide, dihexyl aluminum iodide, dioctyl aluminum fluoride, dioctyl aluminum chloride, dioctyl aluminum bromide, dioctyl aluminum iodide, ethyl aluminum difluoride, d Le aluminum dichloride,
Examples include ethyl aluminum dibromide, ethyl aluminum diiodide, isobutyl aluminum dichloride, methyl aluminum sesquichloride, ethyl aluminum sesquichloride, aluminum trichloride, aluminum tribromide, aluminum triiodide.

Further, as the alkylaluminum alkoxide, the general formula AlR ⁵ _q (OR ⁶ ) _3-q (in the formula, R ⁵ and R ⁶ are the same or different alkyl groups, q
Represents an alkoxyl derivative of an organoaluminum compound represented by 1 or 2. Among these, examples of the alkyl group include linear or branched alkyl groups having 1 to 8 carbon atoms, such as methyl group, ethyl group, n-butyl group, isobutyl group, hexyl group, and octyl value.

Preferred specific examples of alkylaluminum alkoxides include diethylaluminum monomethoxide, diethylaluminum monoethoxide, diethylaluminum monobutoxide, diisobutylaluminum monomethoxide, diisobutylaluminum monobutoxide, ethylaluminium dioxide. Examples thereof include methoxide, ethyl aluminum dietoxide, ethyl aluminum dibutoxide, isobutyl aluminum dimethoxide, isobutyl aluminum dietoxide, isobutyl aluminum dibutoxide and the like.

Among the above other aluminum compounds, trimethyl aluminum, diethyl aluminum chloride, ethyl aluminum sesquichloride, ethyl aluminum dichloride, diethyl aluminum monoethoxide, diethyl aluminum monoethoxide, ethyl aluminum monoethoxide, and ethyl aluminum die Toxide is preferred because it has high catalytic activity when used in combination with aluminoxane.

The ratio of aluminoxane used to other aluminum compounds is 100 / aluminum atomic ratio.
It is 0 to 25/75. The other aluminum compounds mentioned above are used in combination with aluminoxane and used in one kind or in two or more kinds.

The amount of the catalyst used in the present invention is such that the organic acid salt of cobalt (A) is 0.001 to 1 mmol, preferably 0.01 to 1 per mol of conjugated diene. It is about 0.5 mmol.
The amount of the (B) phosphine compound used is usually 0.1 to 50, preferably 0.1 to 20, more preferably 0.1 to 50 as the ratio (P / Co) of phosphorus atoms to cobalt atoms of the component (A). It is 0.1 to 10. If this ratio is less than 0.1 or more than 50, the polymerization activity decreases. further,
The amount of organoaluminum (C) used is usually 4 to 10 ⁵ , preferably 10 to 10 ⁴ , as the ratio (Al / Co) of aluminum atoms to cobalt atoms of the organic acid salt of cobalt (A).

The catalyst used in the present invention may further contain a polymerization activator such as an ester compound, an alcohol compound, a phenol compound, a sulfoxide compound, a nitrogen-containing heterocyclic compound, water and a tertiary amine compound, if necessary. You may add. The addition amount of this polymerization activator is 10 ⁻³ to 10 molar equivalents relative to the Al atom of the organoaluminum (C).

The catalyst used in the present invention is prepared by mixing the catalyst components in any order in an inert organic solvent. Preferably, when the component (A) and the component (B) are mixed and prepared in advance, a highly active catalyst can be stably formed. Further, it is preferable that the component (C) is mixed in advance and brought into contact with the components (A) to (B) in the reaction system. The catalyst may be prepared by mixing the respective components in advance before contacting the catalyst with the conjugated diene containing 1,3-butadiene as the main component of the present invention. It can also be prepared by mixing the components in the presence of a diene.

In the present invention, the conjugated diene containing 1,3-butadiene as a main component is added to the catalyst, that is, (A) to (C).
Polymerization is carried out in an inert organic solvent using a catalyst containing the component as the main component. Examples of the inert organic solvent used as the polymerization solvent include aromatic hydrocarbon solvents such as benzene, toluene, xylene, and cumene, butane, pentane, aliphatic hydrocarbon solvents such as hexane, cyclopentane, methylcyclopentane, and cyclohexane. Alicyclic hydrocarbon solvent, methylene chloride, chloroform, carbon tetrachloride, 1,2
-Halogenated hydrocarbon solvents such as dichloroethane, trichloroethylene, perchlorethylene, chlorobenzene, bromobenzene, chlorotoluene and the like and mixtures thereof are mentioned, preferably aliphatic and alicyclic hydrocarbon solvents.

The polymerization temperature is usually -50 to 120 ° C,
It is preferably -20 to 80 ° C. The polymerization reaction may be a batch system or a continuous system. The monomer concentration in the solvent is
Usually, it is 5 to 80% by weight, preferably 10 to 50% by weight. Further, in order to produce a polymer, in order not to deactivate the catalyst of the present invention and the polymer, consideration should be given so as to minimize mixing of a compound having a deactivating action such as oxygen, water or carbon dioxide gas into the polymerization system. is necessary. When the polymerization reaction has proceeded to the desired stage, the reaction mixture is added with alcohol, another polymerization terminator, an antioxidant, an antioxidant, an ultraviolet absorber, etc., and then the produced polymer is separated, washed and dried according to a usual method. Thus, the desired butadiene-based polymer can be obtained.

The butadiene-based polymer obtained by the production method of the present invention has a vinyl bond content of 8 in the butadiene portion.
It is 0% or more, preferably 85% or more. The melting point (Tm) of the butadiene-based polymer obtained by the present invention is 50.
It is a polymer containing a crystal structure at 150 ° C.

Further, the glass transition temperature (Tg) of the butadiene polymer obtained in the present invention is -30 to 10 ° C. As described above, according to the present invention, a cobalt-based catalyst in which a specific ligand is combined can provide a butadiene-based polymer having a low glass transition temperature and excellent low-temperature characteristics without impairing the decrease in melting point. In other words, the low temperature range of use can be widened. In particular, when the present invention is applied to a high melting point polymer system, impact resistance at low temperature, which has been a drawback in the past, can be greatly improved. That is, as the melting point is increased, the glass transition temperature is conventionally increased, and Tg
The ratio of (K) / Tm (K) is constant for the catalyst used,
The catalyst system of the present invention can exhibit the effect of greatly changing this ratio as compared with the conventional catalyst system. In addition,
In the present invention, Tg of the obtained butadiene-based polymer
(K) / Tm (K) is preferably 0.630 to 0.7.
50.

Further, the molecular weight of the butadiene-based polymer obtained in the present invention can be varied over a wide range, but its polystyrene-equivalent weight average molecular weight is
Usually, it is 10 ⁴ to 10 ⁶ , and if it is less than 10 ⁴ it is not preferable because it is inferior in strength properties, while if it exceeds 10 ⁶ it is inferior in processability and excessive torque is applied during kneading with a roll or Banbury, It is not preferable because the dispersion of the compounding agent or the reinforcing agent such as carbon black is poor and the performance of the vulcanized product is deteriorated.

Further, the butadiene-based polymer obtained in the present invention has a molecular weight distribution (M) represented by the ratio of polystyrene-equivalent number average molecular weight (Mn) and weight average molecular weight (Mw).
w / Mn) can also be maintained, usually 1.5-5.
It can be controlled in the range of 0.

The butadiene-based polymer obtained by the present invention is blended as a raw rubber with the polymer alone or blended with other synthetic rubber or natural rubber, and if necessary, oil-extended with a process oil, and then, A rubber composition which is obtained by adding a filler such as carbon black, a vulcanizing agent and a usual vulcanizing compounding agent such as a vulcanization accelerator into a rubber composition, and vulcanizing the composition to obtain mechanical properties and abrasion resistance. It can be used for applications such as tires, hoses, belts, sponges, footwear materials, sheets, films, tubes, packaging materials, resin modifiers, photosensitive materials, and various other industrial products.

[0037]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, parts and% are based on weight unless otherwise specified.
Further, various measurements in the examples were based on the following methods.
The vinyl bond content of the butadiene-based polymer was determined by an infrared absorption spectrum method (Morero method). The melting point (Tm) and glass transition temperature (Tg) of the butadiene-based polymer are
Using a DSC (differential scanning calorimeter), ASTM D341
It measured according to 8. The weight average molecular weight and the number molecular weight are determined by gel permeation chromatography (GP
C) [manufactured by Shimadzu Corporation, C-4A], 40
C. and tetrahydrofuran were used as the solvent.

Example 1 Under a dry nitrogen atmosphere, 40 g of n-hexane and 10 parts of 1,3-butadiene were placed in a hard pressure-resistant bottle having an internal volume of 100 ml.
g, 10% toluene solution of methylaluminoxane (MAO), cobalt 2-ethylhexylate, and a mixed solution of tricyclohexylphosphine and triphenylphosphine (phosphine compound) in toluene, 1,3-butadiene (BD) / 2-ethylhexyl Cobalt acid (Co organic acid salt) (molar ratio) = 20,000, tricyclohexylphosphine / triphenylphosphine (molar ratio) = 80 /
20, phosphine compound / Co organic acid salt (P / Co atomic ratio) = 2.0, methylaluminoxane / Co organic acid salt (Al / Co atomic ratio) = 100, and added with a shaker. Polymerization was carried out at 10 ° C. for 30 minutes while mixing in the system. The reaction was stopped by adding a small amount of methanol containing 2,6-di-t-butyl-p-cresol as a terminating agent to the reaction system. Then, as a coagulant,
The polymer was separated using a large amount of methanol containing 2,6-di-t-butyl-p-cresol. After collection by filtration
It was vacuum dried at 40 ° C., and the polymer yield was determined from the yield. The results are shown in Table 1.

Examples 2 to 4 Polymerization was carried out under the same conditions and operations as in Example 1, except that the addition amount ratio of tricyclohexylphosphine / triphenylphosphine used in Example 1 was changed as shown in Table 1. went. The results are shown in Table 1. Examples 5 to 8 Polymerization was performed in the same manner as in Example 1 except that the combination of the phosphine compound used in Example 1 was replaced with tricyclohexylphosphine and tri (3-methylphenyl) phosphine. The results are shown in Table 1.

Example 9 The combination of the phosphine compounds used in Example 1 was changed to 40/3 of tricyclohexylphosphine, triphenylphosphine and tri (3-methylphenyl) phosphine.
Polymerization was performed in the same manner as in Example 1 except that the composition molar ratio was changed to 0/30. The results are shown in Table 1. Example 10 Polymerization was performed in the same manner as in Example 1 except that the phosphine compound used in Example 1 was replaced with dicyclohexylphenylphosphine. The results are shown in Table 1.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that the mixed phosphine used in Example 1 was replaced with triphenylphosphine.
The results are shown in Table 1. Comparative Example 2 Polymerization was performed in the same manner as in Example 1 except that tri (3-methylphenyl) phosphine was used instead of the mixed phosphine used in Example 1. The results are shown in Table 1. Comparative Example 3 Polymerization was performed in the same manner as in Example 1 except that tricyclohexylphosphine was used instead of the mixed phosphine used in Example 1. The results are shown in Table 1. Comparative Examples 4 to 7 Table 1 shows the melting points and glass transition temperatures of commercially available crystalline 1,2-polybutadiene (trade name JSRRB manufactured by Japan Synthetic Rubber Co., Ltd.).

[0042]

[Table 1]

As is clear from Table 1, Examples 1-10
Since a mixed ligand is used as a phosphine compound, a butadiene-based polymer having a low glass transition temperature, in other words, a crystalline high vinyl bond having excellent low-temperature characteristics is obtained. On the other hand, in Comparative Examples 1 and 2, those having a high melting point were obtained, but the glass transition temperature was high accordingly. Further, in Comparative Example 3, no melting point is recognized. Further, Comparative Examples 4 to 7 are all commercially available 1,2-polybutadienes up to now, which have high vinyl bonds but low melting points. The Tm and T of the obtained polymer
The relationship of g is shown in FIG. The method for producing the polymer of the present invention is
As is clear from FIG. 1, even if the Tg of the polymer of the example is compared with the Tm of the polymer of the comparative example, a polymer having a low Tg can be obtained.

[0044]

INDUSTRIAL APPLICABILITY According to the present invention, by using a phosphine compound composed of a ligand component having a specific structure as a catalyst system, the use system of triarylphosphine ligands and the conventional commercially available crystalline 1, With respect to the relationship between the melting point of 2-polybutadiene and the glass transition temperature, a butadiene-based polymer having a low glass transition temperature, in other words, a high vinyl bond having excellent low-temperature characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between Tm and Tg of a butadiene-based polymer.

[Explanation of symbols] Tm melting point (° C) Tg glass transition temperature (° C)

Claims (1)

[Claims] 1. A mixed distribution of a conjugated diene containing 1,3-butadiene in an amount of at least 50 mol%, which comprises (A) an organic acid salt of cobalt, (B) an alicyclic hydrocarbon phosphine and an aromatic hydrocarbon phosphine. A method for producing a butadiene-based polymer having a high vinyl bond, which comprises polymerizing in an inert organic solvent using a catalyst containing a ligand and an organoaluminum containing (C) aluminoxane.