JPH06192310A - Production of polymer - Google Patents

Abstract

PURPOSE:To produce a polymer having small hysteresis loss and excellent processability in high productivity by polymerizing a conjugated diene, etc., in a hydrocarbon solvent using an organolithium compound as a starting agent and adding an organometallic compound to the reactional system in the chain- extension stage of the polymerization process. CONSTITUTION:A conjugated diene and/or a vinyl aromatic hydrocarbon are polymerized in a hydrocarbon solvent in the presence of an organolithium compound as an initiator. In the polymerization chain-extension stage of this polymerization process, an organometallic compound of the formula (M is tin, germanium or lead; R is 1-30C aliphatic, alicyclic or aromatic hydrocarbon group; (n) is >=1) is added to the polymerization system. The solvent is benzene, etc., and the monomer is 1,3-butadiene, isoprene, styrene, etc. The organometallic compound is preferably diphenyltin monomer, cyclic dibutyltin tetramer, etc. The amount of the organometallic compound is 0.7-5mol-equivalent based on 1mol of the terminal lithium having polymerization activity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a polymer which has a small hysteresis loss and is excellent in workability and can be obtained with high productivity.

[0002]

2. Description of the Related Art In recent years, automobiles are required to have low fuel consumption. Therefore, a rubber having a small hysteresis loss and good workability is desired as a rubber for a tire material. Therefore, natural rubber, polyisoprene rubber, polybutadiene rubber, or the like, which is known as a rubber material having a small hysteresis loss, is used. Further, as a synthetic rubber having a significantly improved low hysteresis loss, there is a polymer prepared by polymerizing an organolithium compound as an initiator in a hydrocarbon solvent and coupling a tin halide compound to the end of the polymer (JP-A-57-5).
5912). This polymer is a polymer having very excellent physical properties, and is used in a rubber composition for a tire having low rolling friction resistance and low fuel consumption.

In the method for producing this polymer, when a tin halide compound is used to cause a coupling reaction at the terminal of the polymer, the polymerization reaction system becomes inactive at the stage when the tin compound is added, and the residual monomer remains. It is considered that it remains unreacted, and the molecular structure of the obtained polymer is determined at the time when the tin compound is added, and since it has a molecular structure containing tin in the molecular chain, the reaction surface, that is, economical efficiency. From the viewpoint of, and both sides of the molecular structure, that is, from the viewpoint of molecular design, in order not to leave unreacted monomer,
A tin compound is added when the polymerization reaction is completed.

[0004]

As described above, in the conventional method for producing a polymer using a modifier such as a coupling agent such as a tin halide compound, the modifier is added after the polymerization, and , Even if there is unreacted monomer remaining at this point, the batch polymerization method is adopted, which is followed by the step of recovering the target polymer, but the batch polymerization method has poor productivity as compared with the continuous polymerization method, There is a problem that the production cost is increased, and as a result, the polymer is expensive.

On the other hand, various other continuous polymerization methods are known, but at the same time, a method for producing a polymer having a small hysteresis loss and excellent workability has not yet been known.

Further, according to the conventional method by the coupling reaction between the active terminal lithium of the polymer and the tin halide compound, even if the tin halide compound is reacted in an amount equivalent to the active lithium, the reaction is theoretically 100%. Does not occur, and industrially remains at about 60%.
That is, it cannot be said that the conventional method is sufficient even if a polymer having a small hysteresis loss is obtained.

Further, the conventional polymer obtained by coupling a polymer having an active terminal with a metal halide compound or the like can improve various properties, but on the other hand, it has a very high molecular weight polymer. Therefore, it has a drawback that the workability becomes difficult.

Therefore, in order to solve the above problems, the present invention has a new idea of using an organometallic compound different from the conventional one, so that the coupling efficiency is high, that is, the hysteresis loss is small, the workability is excellent, and the production is high. It is an object to provide a novel method for producing a polymer that can be obtained with good properties.

[0009]

The method for producing a polymer according to claim 1, wherein a conjugated diene and / or a vinyl aromatic hydrocarbon is polymerized in a hydrocarbon solvent with an organolithium compound as an initiator to carry out polymerization. It is characterized in that the organic metal compound represented by the following general formula is added to the polymerization system to carry out the polymerization reaction immediately after the start and before the end of the polymerization chain growth.

[0010]

[Chemical 2]

(M: a metal selected from tin, germanium and lead, R: an aliphatic, alicyclic or aromatic hydrocarbon group having 1 to 30 carbon atoms, n: an integer of 1 or more; The compound represented by is abbreviated as (R ₂ M) _n ) The present inventors have proposed a polymerization reaction with an organolithium, an interaction between this polymerization active terminal lithium and an organometallic compound, and a reactivity of the interaction generation system As a result of repeated intensive investigations, surprisingly, the polymerization reaction did not end even when an organometallic compound was added to the system after the initiation of polymerization, and a polymer containing a metal-carbon bond chain was produced. I found that. The mechanism is considered to be Equation 1 below.

[0012]

[Equation 1]

That is, when the organometallic compound (b) of the present invention is added to the polymer (a) during the formation of the polymerization chain, a coupling reaction occurs to produce a metal-carbon bond chain-containing polymer (c),
Since this has the ability to initiate polymerization, polymerization of the monomer occurs continuously, the chain grows and low hysteresis loss metal-carbon bond chain-containing high molecular weight polymer (d) is obtained, (d)
Since has an active end, it can easily react with a denaturing agent. At this time, a single or plural R ₂ M, that is, the number of m is inserted in (c). During the kneading, the polymer (d) is cut by the stearic acid and heat to break between PM and between MP ', thereby exhibiting various characteristics. Focusing on P obtained by cutting,
The molecular weight of P can be easily adjusted by the addition timing and the addition amount of (b) after the initiation of the polymerization, and does not change to the polymer (d). Similarly for the molecular weight of P ',
It is adjusted depending on the addition timing and amount of (b). If these are controlled to a low molecular weight polymer having an appropriate molecular weight,
This low molecular weight polymer makes the polymer of the present invention extremely excellent in processability.

More specifically, for example, when random copolymerization of butadiene and styrene is carried out in a hydrocarbon solvent using an ether compound or the like with a butyllithium compound as an initiator, one example is given at the initial stage of chain formation. As the addition of dibutyltin tetramer as, if there is a polymerization active terminal lithium that does not participate in the coupling reaction with this organotin compound in the system, the polymerization at the active point continues, but at the same time, the polymerization active terminal lithium and organic The tin-carbon bond chain-containing polymer produced by the coupling reaction with the tin compound is newly endowed with polymerization ability, and as long as there is an unreacted monomer, the growth of the polymerization chain continues, and high molecular weight tin- A carbon-bonded chain-containing random butadiene-styrene copolymer is obtained, and this polymer is excellent in processability. Et obtained vulcanized rubber was found that the small effect of the hysteresis loss were conspicuously observed, and have completed the present invention.

The present invention will be described in more detail below. In the production method of the present invention, those used as a polymerization solvent include, for example, aromatic hydrocarbon solvents such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as n-pentane, n-hexane and n-butane, Methylcyclopentane,
Alicyclic hydrocarbon solvents such as cyclohexane and mixtures thereof can be used.

The organolithium compound used as an initiator in the present invention includes n-butyllithium, ethyllithium, propyllithium, tert-butyllithium, hexyllithium, 1,4-dilithiobutane, butyllithium and divinylbenzene. Examples thereof include alkyllithium, alkylenedilithium, phenyllithium, stilbendilithium and the like. Preferably,
It is n-butyl lithium or tert-butyl lithium. Even if these organolithium initiators are used alone, 2
You may use it in mixture of 2 or more types. The amount of these organic lithium compounds used is 0.2 to 30 per 100 g of the monomer.
It can be used in the range of mmol.

To obtain the polymer of the present invention, the monomers used for the polymerization are conjugated dienes and / or vinyl aromatic hydrocarbons, the conjugated dienes having 4 to 12 carbon atoms per molecule, preferably It is a conjugated diene hydrocarbon containing from 4 to 8. Examples thereof include 1,3-butadiene, isoprene, piperylene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and octadiene. These may be used alone or in combination of two or more, and 1,3-butadiene is particularly preferable.

The vinyl aromatic hydrocarbon includes styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, p-butylstyrene, vinylnaphthalene and the like, and particularly styrene. preferable.

The structural formula (R₂M)_nRepresented by
In organic metal compounds, M in the formula is tin, germanium and
And a metal selected from lead, where R is a carbon number of 1 to 30
Represents an aliphatic, alicyclic or aromatic hydrocarbon group of
Represents an integer of 1 or more. (R ₂M)_nWhere n = 1
And in the case of 2 and R respectively₂M monomer and MM bond
Represents a dimer having, and in the case of n ≧ 3, MM bond
Cyclic polymers such as trimers and tetramers that form a ring with
Represents Preferred among M is tin. Also in R
Of these, preferred is the above hydrocarbon group having 1 to 20 carbon atoms.
Yes, for example, methyl, ethyl, propyl, n-but
Tyl, sec-butyl, tert-butyl, octyl, cyclo
Hexyl, cyclopentadienyl, phenyl, tolyl,
List xylyl, naphthyl, and phenanthryl groups.
You can The possible values of n depend mainly on the type of R.
R₂It is not uniform because the reactivity of M is different,
Although not specified, 1 to 6 is generally preferable. (R₂
M)_nFor example, M is tin and R is exemplified above.
R which is a hydrocarbon group₂M monomer (n = 1), dimer
-(N = 2), oligomer (3≤n≤6)
For example, diphenyl tin monomer, dibutyl tin
Z-tetramer, di-tert-butyltin tetramer, dime
Chill tin hexamer (dodecamethyl cyclohexa stana
), Diphenyltin hexamer, di- (2,4,6-triyl
Sopropylphenyl) tin trimer is included.

The addition amount of the organometallic compound represented by the structural formula (R ₂ M) _n of the present invention is 0.1 to 10 mol as (R ₂ M) _{n with} respect to 1 mol equivalent of the polymerization active terminal lithium. It is an equivalent, preferably 0.7 to 5 molar equivalents. If the amount added is less than 0.1 molar equivalent, chain growth of the metal-carbon bond chain-containing polymer will occur, but the polymerization will proceed at a high frequency regardless of this mechanism. The ratio of the metal-carbon bond chain-containing polymer in the polymer decreases, and the desired physical properties become poor, which is not preferable.
On the other hand, even if the amount added exceeds 10, polymerization by this mechanism can be continued without deactivating the active terminal lithium, but this is not preferable in terms of reaction rate and the like. The addition may be simultaneous or continuous.

In the present invention, the timing of addition of the organometallic compound is an important factor for achieving the object of the present invention, and is added to the polymerization system immediately after the initiation of the polymerization with the organolithium compound and before the termination of the polymerization. Is added.

In the present invention, the polymerization activity is improved and / or
Ordinarily used for this purpose in order to adjust the molecular structure of the desired polymer (molecular weight, microstructure, in the case of a copolymer, in addition to this, the composition of monomer units and its composition distribution, etc.) according to the application. Additives such as Lewis bases such as ether compounds and tertiary amine compounds can be added to the reaction system. Examples of the ether compound used include diethyl ether, dibutyl ether, tetrahydrofuran, 2-methoxytetrahydrofuran, 2-methoxyethyl tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether. , Diethylene glycol dibutyl ether, triethylene glycol dimethyl ether and the like. Further, as the tertiary amine compound, triethylamine, tripropylamine, pyridine, N,
N, N ', N'-tetramethylethylenediamine, N,
N, N ', N'-tetraethylethylenediamine, N-methylmorpholine, etc. are mentioned. The ether compound and the tertiary amine compound are used in an amount of 0.05 to 1000 mol per mol of the organic lithium compound.

In the production of the polymer of the present invention, when the continuous polymerization method of the present invention has to be interrupted or terminated due to the convenience of the process, or when the molecular design is changed to impart desired physical properties to the polymer, etc. In addition, after completing the polymerization reaction, at least one compound selected from a silicon compound, a tin compound, an isocyanate group-containing compound in the molecule or a compound containing -CM-N <bond (M: O or S) is used as a modifier. It can be added.

Examples of the silicon compound include silicon tetrachloride, chlorotriethylsilane, chlorotriphenylsilane, dichlorodimethylsilane and the like.

Examples of the tin compound include tin halides such as tin tetrachloride and tin tetrabromide, and organotin halides such as diethyldichlorotin, dibutyldichlorotin, tributyltin chloride, diphenyldichlorotin and triphenyltin chloride. A compound etc. are mentioned.

Examples of the above-mentioned isocyanate group-containing compound include phenyl isocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate and dimer and trimer aromatic poly (s) thereof. Isocyanate compounds can be mentioned.

Examples of the compound containing -CM-N <bond (M: O or S) include formamide, N, N-dimethylformamide, acetamide, N, N-diethylacetamide, aminoacetamide, N, N-dimethyl-.
N ', N'-dimethylaminoacetamide, N, N-dimethylaminoacetamide, N, N-dimethyl-N'-ethylaminoacetamide, acrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, nicotinamide , Isonicotinamide, picolinic acid amide, N, N-dimethylisonicotinamide, succinic acid amide, phthalic acid amide, N, N, N ′, N′-tetramethylphthalic acid amide, oxamide, N, N, N ′ ,
N′-tetramethyloxamide, 1,2-cyclohexanedicarboximide, 2-furancarboxylic acid amide,
Amide compounds such as N, N-dimethyl-2-furancarboxylic acid amide, quinoline-2-carboxylic acid amide, N-ethyl-N-methyl-quinolinecarboxylic acid amide, succinimide, N-methylsuccinimide, maleimide, N- Imide compounds such as methylmaleimide, phthalimide and N-methylphthalimide, ε-caprolactam, N-methyl-ε-caprolactam, 2-pyrrolidone, N-methyl-
Lactam compounds such as 2-pyrrolidone, 2-piperidone, N-methyl-2-piperidone, 2-quinolone, N-methyl-2-quinolone, urea, N, N′-dimethylurea,
Urea compounds such as N, N-diethylurea, N, N, N ', N'-tetramethylurea, N, N-dimethyl-N', N'-diphenylurea, N, N'-dimethylethyleneurea,
Carbamate derivatives such as methyl carbamate, N, N-diethyl carbamate, isocyanuric acid, N,
Examples thereof include isocyanuric acid derivatives such as N ′, N ″ -trimethylisocyanuric acid and their corresponding thiocarbonyl-containing compounds, etc. The modifier is not particularly limited as long as it is a compound that reacts with the active end of the polymer chain.

The polymerization temperature is usually from -20 to 150 ° C,
It is preferably 0 to 120 ° C. The monomer concentration in the solvent is usually 5 to 50% by weight, preferably 10 to 3%.
It is 5% by weight. In the case of copolymerization of conjugated diene and vinyl aromatic hydrocarbon, the content of vinyl aromatic hydrocarbon in the charged monomer mixture is 3 to 50% by weight, preferably 5 to 40% by weight.
% By weight.

The polymerization reaction is carried out by contacting the monomer in the liquid phase with the catalyst, but it is usually preferred to operate at a pressure sufficient to maintain the liquid phase in nature.
In addition, it is preferable to exclude substances interfering with the catalytic action from all the above substances charged into the reaction system.

After the reaction is completed, steam is blown into the polymer solution to remove the solvent, or a poor solvent such as methanol is added to coagulate the polymer, and then the polymer is dried on a hot roll or under reduced pressure to form the polymer. Obtainable. Alternatively, the polymer solution can be obtained by directly removing the solvent from the polymer solution on a hot roll or under reduced pressure.

The polymer of the present invention is a polymer containing a high molecular weight polymer containing a metal-carbon bond chain, and is a homopolymer of a conjugated diene or a vinyl aromatic hydrocarbon, a conjugated diene and a vinyl aromatic hydrocarbon. And a mixture of both polymers. Particularly useful is a high molecular weight polybutadiene or a butadiene-styrene copolymer, and the molecular weight of the high molecular weight polymer having a metal-carbon bond chain contained therein can be arbitrarily controlled depending on the application.

In the polymer of the present invention, the ratio of the high molecular weight polymer containing a metal-carbon bond chain to the polymer not containing a metal-carbon bond chain in the whole polymer is preferably 50% or more. If it is less than 50%, a sufficient effect cannot be expected in the low hysteresis loss property.

Taking polybutadiene or a butadiene-styrene copolymer as an example, the butadiene part has a microstructure (cis-1,4, trans-1,4, vinyl), and a butadiene / styrene copolymer. Composition, its composition distribution (random structure, block structure or mixed structure)
Can easily obtain a polymer having a molecular structure freely selected according to the purpose, and can be applied to various uses.

The butadiene-styrene copolymer of the present invention may be used alone or in a blend with a natural rubber or a synthetic rubber,
If necessary, extend the oil and add the usual compounding agents for vulcanized rubber,
Vulcanized and used for tire applications, anti-vibration rubber, belts, hoses, and other industrial products.

[0035]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

In the examples, parts and% mean parts by weight and% by weight unless otherwise specified.

Various measurements were made by the following methods. The weight average molecular weight of the polymer is measured by gel permeation chromatography (GPC), and the differential refractive index (R
I) and the ultraviolet absorptance (UV) at 254 nm were used, and the conversion was performed in terms of polystyrene using monodisperse polystyrene as a standard.

The microstructure of the butadiene portion of the styrene-butadiene copolymer was determined by the infrared method (Morero method). The bound styrene content was determined from the calibration curve by infrared method based on the absorption of the phenyl group at 699 cm ^-1 .

There are various methods of measuring the concentration of lithium at the polymerization active terminal used for calculating the molar equivalent ratio of the tin halide compound and lithium, but the concentration was 68 mol% of the organolithium initiator charged at the start of the polymerization. In the polymerization using the organolithium initiator, the solvent and the like are used after sufficiently purified in advance, but in ordinary polymerization, a part of the organolithium initiator is water, carbon dioxide, etc. in the polymerization system. Will be deactivated due to the impurities. Generally, in the polymerization of a conjugated diene and / or a vinyl aromatic hydrocarbon having an organolithium compound as an initiator as in the present invention, the molecular weight distribution is sufficiently narrow as about 1.1, and therefore, theoretically, the polymerization is performed. It is known that the number average molecular weight (Mn) of the polymer is established as the following formula A (Takayuki Otsu, “Experimental Method of Polymer Synthesis” p212, Kagaku Dojin).

[Formula A] Mn = [(number of moles of monomer) / (number of moles of organolithium initiator)] × (molecular weight of monomer) It is known that the formula A is substantially valid in the polymerization experiment carried out in the present invention. Due to impurities, the organolithium concentration at a certain ratio is assumed as in Equation B.

[Formula B] (Activation Polymerization Terminal Lithium Concentration) = (Effective Organolithium Initiator Mol Number) = (Molecule of Organolithium Initiator Charged at the Beginning of Polymerization) × (Organic Lithium Residual Rate) When using the same lot of solvent and polymerized monomer, it is clear that the process of Formula B is established, and this formula is used industrially and empirically. There is something. Therefore, a preliminary experiment was conducted before conducting the series of examinations this time, and equations A and B were used.
The residual rate of organolithium determined by using was determined to be 68%. Therefore, the concentration of active polymerization terminal lithium was set to 68% of the number of moles of the organolithium initiator charged in the polymerization initiator.

As an index of the processability of the polymer, the compound of the polymer was rolled into a 3-inch roll at 50 ° C., and the winding property of the roll was visually evaluated.

Tan δ was used as an index of hysteresis loss in the vulcanized polymer. The smaller tan δ,
It is evaluated as low hysteresis loss. The tan δ was measured using a viscoelasticity measuring device (manufactured by Rheometrics) at a temperature of 50 ° C., a strain of 1% and a frequency of 15 Hz.
The tensile properties were measured according to JIS K6301.

In the present embodiment, the structural formula (R ₂ M) _n
As the organometallic compound represented by, a dibutyltin compound represented by dibutyltin tetramer [(Bu ₂ Sn) ₄ ] was used.

Generally, the structural formula (R₂Sn)_nRepresented by
As for the manufacturing method of the tin compound, various methods are considered.
To be For the specific method, see the review by Robert K. Ingham et al.
(Chemical Reviews, 1960,60, 517) As shown in Equation 2 below
(1) Reaction of Grignard reagent with tin dichloride
(2) Reaction of organic lithium with tin dichloride (3) R₂S
nX ₂The reaction between alkali metal and
It

[0046]

[Equation 2]

The dibutyltin compound used in this example is
It was synthesized by adopting the method of (3). Specifically, Argo
0.4 mol of lithium metal in a glass atmosphere
Pre-prepared dibutyltin dichlora placed in a vessel
Id 0.2 mol, tetrahydrofuran (THF) 150
g of dibutyltin dichloride / THF solution
And perform the reaction while stirring at -20 ° C for 3 hours.
It was Obtained (R₂Sn) _nTo¹¹⁹Analysis by Sn-NMR
As a result, a peak was observed at -197.7 ppm. Well
In addition, by using inductively coupled plasma optical emission spectrometry,
The amount of tin in rutin chloride was obtained (R₂Sn)_nof
As a result of measuring the amount of tin, the above reaction was almost 100% in yield.
It was concluded that there is. Further obtained (R₂Sn)_nMolecule
When the amount was measured by GPC, a monodisperse peak was obtained.
It was concluded that its molecular weight was n = 4.

Therefore, the organotin compound obtained here was a cyclic tetramer of dibutyltin.

Example 1 A reactor equipped with a stirrer of 5 liters was charged with 1,500 g of cyclohexane, 200 g of 1,3-butadiene, 50 g of styrene and 0.800 g of THF, and the temperature inside the reaction vessel was adjusted to 60 ° C. Butyllithium (0.140 g) was added to initiate polymerization.

Immediately after charging n-butyllithium and initiating the polymerization, it was obtained by the above method (Bu ₂ S).
n) ₄ 0.174 g was added. After that, further polymerization is 6
After 60 minutes at 0 ° C., the polymerization was stopped with isopropyl alcohol.

Next, 2,6-di-te was added to the polymer-containing liquid.
After adding 2.5 g of rt-butyl-p-cresol, the solvent was removed by steam stripping, and the obtained solid was
A rubbery polymer was obtained by drying with a hot roll at 00 ° C.
The properties of the polymer are shown in Table 1.

The polymer was 25 according to the formulation shown in Table 3.
Kneading with 0 ml Labo Plastomill and 3 inch roll,
After compounding, the processability (rolling property) was evaluated, and this compound was vulcanized at 145 ° C. for 35 minutes. Table 2 shows the evaluation results of the processability and the physical properties of the vulcanized products.

[Examples 2 to 4] The same procedure as in Example 1 was carried out except that the addition amounts of the organotin compound were 0.346 g, 0.693 g and 1.386 g. The properties of the polymer, the processability of the blend and the physical properties of the vulcanizate are shown in Tables 1 and 2.

Comparative Example 1 Polymerization was carried out in exactly the same manner as in Example 1 except that the organotin compound was not added. The properties of the polymer, the processability of the blend and the physical properties of the vulcanizate are shown in Tables 1 and 2.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

As shown in Tables 1 and 2, butadiene-
As a coupling agent at the initial stage of styrene copolymerization,
Examples 1 to 4 to which the cyclic organotin compound was added showed excellent values in all of elongation, tensile strength, tan δ and roll wrapping property, as compared with Comparative Example 1 in which this compound was not added, The polymer was well-balanced in terms of processability, breaking properties, low hysteresis loss, and the like.

As described above, despite the addition of the organotin compound at the initial stage of the polymerization, the polymerization proceeds stoichiometrically as in the ordinary living polymerization of Comparative Example 1, and a continuous polymerization system is possible. It is noteworthy that a high-molecular weight butadiene-styrene random copolymer containing a considerable amount of a high-molecular weight tin-carbon bond chain-containing polymer was obtained.

[0060]

Since the method for producing a polymer of the present invention has the above-mentioned constitution, it has an excellent effect that a polymer having excellent processability and a low hysteresis loss can be obtained with high productivity.

Claims (1)

[Claims] 1. A polymerization system in which a conjugated diene and / or a vinyl aromatic hydrocarbon is polymerized in a hydrocarbon solvent using an organolithium compound as an initiator and immediately after the initiation of the polymerization until the end of the polymerization chain growth period. A method for producing a polymer, which comprises adding an organometallic compound represented by the following general formula to carry out a polymerization reaction. [Chemical 1] (M: a metal selected from tin, germanium and lead,
R: an aliphatic, alicyclic or aromatic hydrocarbon group having 1 to 30 carbon atoms, n: an integer of 1 or more)