JPH05331222A - Production of polymer - Google Patents

Abstract

PURPOSE:To efficiently obtain a polymer having low hysteresis loss by adding a specific organometallic compound to a polymerization system in polymerizing a conjugated diene and/or a vinyl aromatic hydrocarbon using an organolithium compound as an initiator. CONSTITUTION:An organometallic compound of the structural formula MR4 (M is metal selected from tin, germanium and lead and preferably tin; R is a molecular structural group having a structure selected from allyl, benzyl and phenyl structures in a binding part to M) (e.g. tetraallyltin) is added to a polymerization system during a period just after starting the polymerization and before completing the polymerization, preferably during a polymer chain growth period leading to preferably 80%, more preferably 20% conversion ratio in polymerizing a conjugated diene (preferably 1,3-butadiene) and/or a vinyl aromatic compound (preferably styrene) in a hydrocarbon solvent using an organolithium compound (preferably n-butyl-lithium or t-butyl-lithium) as an initiator to carry out the polymerizing reaction. Thereby, the objective polymer containing a high-molecular weight polymer having tin-carbon bond chain is produced.

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 having a small hysteresis loss with high productivity and at a low cost.

[0002]

2. Description of the Related Art With the demand for low fuel consumption of automobiles, a rubber having a small hysteresis loss is desired as a rubber for a tire material. Natural rubber, cis-1,4 polyisoprene rubber, low cis-
1,4 or high cis-1,4 polybutadiene rubber and the like are known. Further, as a synthetic rubber having remarkably improved hysteresis loss, there is a synthetic rubber obtained by coupling a tin halide compound to a polymer terminal obtained by polymerizing an organic lithium compound as an initiator in a hydrocarbon solvent (for example, JP-A-57-57). 55912). When a coupling reaction is carried out with a tin halide compound at the end of the polymer, the polymerization reaction ends when the tin compound is added, and the reaction system becomes deactivated when the coupling reaction ends. Therefore, it is considered that the polymerization does not continue even if the unreacted monomer remains. On the other hand, considering the molecular structure of the polymer, when the tin compound is added, the molecular structure such as the degree of polymerization of the polymer is determined, and finally the molecular structure of the polymer having tin in the molecular chain is determined. ..

Therefore, in order to prevent the unreacted monomer from being left behind, from the viewpoint of reaction mechanism and economic reasons, and from the viewpoint of molecular design in terms of molecular structure, a tin compound is usually added at the time when the polymerization reaction is completed. Is used.

As described above, in the conventional method using a modifier such as a coupling agent such as a tin halide compound, even if the monomer or the like remains after the modifier is added to the reaction system, It is considered that no reaction can occur anymore or no use is made, and the process for recovering the target polymer is started. That is, a batch polymerization system is adopted.
Compared with continuous polymerization method, batch polymerization method has poor productivity,
This is a big problem because it causes high manufacturing cost and, as a result, the polymer becomes expensive.

On the other hand, when attention is paid only to the continuous polymerization method, as a method of producing a polymer capable of this, a method of producing a blend of polydiene rubber using an organic lithium compound or the like as an initiator (Japanese Patent Laid-Open No. 63-235305). )It has been known. This is because tin-carbon is obtained by adding a certain amount of a branching agent such as tin tetrachloride to the middle stage of the polymerization such as butadiene-styrene copolymerization (conversion rate is 30 to 70%) and coupling 20 to 70% of the polymer. First, a low molecular weight polymer (A) having a bonding chain is produced, and then polymerization is continued with the remaining active terminal lithium to produce a high molecular weight polymer (B) containing no tin-carbon bonding chain. ) A method for producing a polymer blend mainly composed of the polymer (B) with respect to the polymer. This production method is intended to obtain a polymer having improved processability by producing a low molecular weight polymer and a high molecular weight polymer in a polymerization process without using an ordinary blending method.

As another method, a method for improving the processability of polybutadiene or polyisoprene (USP 3,53)
6,691) is known. The purpose of this method is to obtain a polymer having improved processability by adding allyltin as a modifier in the middle stage of the polymerization when the monomer is polymerized in the presence of a special lithium compound, haloaryllithium. That is, this allyl tin was not used to positively introduce a tin-carbon bond chain into the molecular chain of the high molecular weight polymer, and therefore, the effect of enhancing resilience is not recognized at all.
This shows that it is clearly different from the purpose of obtaining a polymer having a small hysteresis loss.

As can be seen from these examples, the continuous polymerization method is known, but at the same time, the method for producing an excellent polymer having a small hysteresis loss is not known.

Further, conventionally, in order to introduce a metal such as tin into a polymer for the purpose of reducing hysteresis loss, a method by means of a coupling reaction between lithium at the active terminal of the polymer and a tin halide compound has been exclusively known. This was inspired by the reaction of lithium with a halogen, but a new idea was to introduce tin into the polymer using a tin compound other than a tin halide compound, for example, an organotin compound, to obtain a polymer with a small hysteresis loss. There is no known way to get it.

[0009]

As described above, there has been a demand for a production method for obtaining an excellent polymer by a continuous polymerization method having high productivity, instead of the batch polymerization method having high production cost.

The present invention is different from the conventional one, and by a new idea using an organometallic compound, a polymer having a small hysteresis loss can be produced with high productivity without impairing the fracture characteristics.
It is an object to provide a novel method for producing a polymer that can be obtained at low cost.

[0011]

The method according to claim 1 is a method for producing a polymer by polymerizing a conjugated diene and / or a vinyl aromatic hydrocarbon with an organolithium compound as an initiator in a hydrocarbon solvent. In, the structural formula MR
₄ (M: metal selected from tin, germanium and lead,
R: an organometallic compound represented by the same or different molecular structure group selected from molecules having an allyl structure, a benzyl structure, and a phenyl structure as a bonding part to M, from the start of polymerization to the end of polymerization chain growth. It is characterized in that it is added to the polymerization system to carry out the polymerization reaction at a certain time.

The inventors of the present invention have conducted an earnest study as a result of paying attention to the polymerization reaction by organolithium, the interaction between this polymerization active terminal lithium and the organometallic compound, and the reactivity of the system for producing the interaction. For example, taking the case where the organotin compound of the present invention is added to the system after the initiation of the polymerization, after the addition, a tin-carbon bond chain-containing polymer is produced, which is activated and the polymerization is initiated in the polymer. It was found that dots were generated and the polymerization of the monomer continued to occur, and the chain grew to give a high molecular weight polymer containing a tin-carbon bond chain. This made it possible to use a continuous polymerization method instead of the batch polymerization method. As described above, this is a new fact that overturns the established theory that the tin-carbon bond chain-containing polymer is conventionally inactive and the monomer polymerization is not continued, so that the batch polymerization method is inevitably adopted.

More specifically, the case where an organotin compound is added when random copolymerization of butadiene and styrene is carried out in a hydrocarbon solvent using a butyllithium compound as an initiator and an ether compound or the like will be exemplified. With the above, if an organotin compound is added after the initiation of the polymerization, if there is a polymerization active terminal lithium that does not participate in the interaction with the organotin compound in the system, the polymerization at the active point continues,
At the same time, the polymerization ability is newly imparted to the tin-carbon bond chain-containing polymer produced by the interaction between the polymerization active terminal lithium and the organic tin compound, and the growth of the polymerization chain continues, resulting in a high molecular weight tin-carbon bond chain. It was found that a random-type butadiene-styrene copolymer was obtained, and the vulcanized rubber obtained from this polymer had a remarkable effect of having a small hysteresis loss. Although the mechanism of imparting the polymerization ability of the tin-carbon bonded chain-containing polymer is unknown, it is considered to be based on a novel mechanism due to the interaction between the polymerization active terminal lithium and the organotin compound of the present invention.

As described above, in the present invention, even after a kind of coupling reaction is carried out by adding the organometallic compound of the present invention in the chain growth stage, that is, in the presence of lithium at the polymerization active terminal, metal such as metal is present as long as the monomer is present. Since the chain growth of the tin-carbon bond chain-containing polymer is continued, a highly productive continuous polymerization method is possible for the first time, and the polymer obtained mainly contains a tin-carbon bond chain-containing high molecular weight polymer. Therefore, it has been revealed that the material has useful physical properties with a small hysteresis loss, and the present invention has been completed.

The present invention will be described in more detail below.
The polymerization solvent is an inert organic solvent, for example, benzene, toluene, an aromatic hydrocarbon solvent such as xylene,
Aliphatic hydrocarbon solvents such as n-pentane, n-hexane and n-heptane, alicyclic hydrocarbon solvents such as methylcyclopentane and cyclohexane, and mixtures thereof can be used.

In the above production method, the organolithium compound used as the initiator is n-butyllithium,
Examples include ethyllithium, propyllithium, tert-butyllithium, hexyllithium, 1,4-dilithiobutane, alkyllithium such as a reaction product of butyllithium and divinylbenzene, alkylenedilithium, phenyllithium, stilbendilithium, and the like. .. Preferred is n-butyl lithium or tert-butyl lithium. These organolithium initiators may be used alone or in combination of two or more. The amount of these organolithium compounds used can be used in the range of 0.2 to 30 mmol per 100 grams of the monomer.

In the present invention, the monomer used for the polymerization is a conjugated diene and / or a vinyl aromatic hydrocarbon, and the conjugated diene contains a conjugated diene containing 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms per molecule. It is a diene hydrocarbon. For example, 1,3-butadiene, isoprene, piperylene, 2,3-dimethyl-1,3-butadiene, 1,3-
Pentadiene, octadiene and the like can be mentioned, and these conjugated dienes can be used alone or in combination of two or more kinds,
Particularly, 1,3-butadiene is preferable.

As the vinyl aromatic hydrocarbon, styrene, α-methylstyrene, p-methylstyrene,
Included are o-methylstyrene, p-butylstyrene, vinylnaphthalene and the like, with styrene being particularly preferred.

In the organometallic compound represented by the structural formula MR ₄ of the method of the present invention, the metal corresponding to M in the formula includes tin, germanium and lead, preferably tin.

Further, the molecular structure group corresponding to R in the formula is
The same or different molecular structure groups selected from molecules having a bond to M with an allyl structure, a benzyl structure and a phenyl structure are applicable.

In the molecular structure group of the molecule having the allyl structure, as the molecular structure, an allyl compound, for example, an allyl, 2-butenyl, 2-pentenyl, cinnamyl, oligomer or polymer having a conjugated diene unit as a bond to M is used. Examples include polybutadiene, butadiene-styrene copolymer, polyisoprene, isoprene-styrene copolymer, and diene-based oligomers thereof. Preferred are allyl, polybutadiene, butadiene-styrene copolymers and diene-based oligomers thereof.

In the molecular structure group of the molecule having the above-mentioned benzyl structure, the molecular structure may be a benzyl compound such as benzyl, α-methylbenzyl, diphenylmethyl,
Oligomer or polymer in which the bonding part to M is a vinyl aromatic hydrocarbon unit, such as polystyrene, styrene-butadiene copolymer, styrene-isoprene copolymer and these styrene-based oligomers are included. Preferred are benzyl, polystyrene, styrene-butadiene copolymers and styrene-based oligomers thereof.

In the molecular structure group of the molecule having the phenyl structure, the molecular structure includes phenyl compounds such as phenyl, toluyl and naphthyl. Preferred are phenyl and toluyl.

Specific examples of the structural formula MR ₄ include tetraallyl tin, tetrapolybutadienyl tin, tetrabenzyl tin, tetrapolystyryl tin, tetraphenyl tin, etc., in which R is the same. Examples of different Rs include allyltriphenyltin and diallyldiphenyltin.

All R's in the structural formula MR ₄ of the present invention are required to be molecular structure groups having an allyl structure, a benzyl structure and / or a phenyl structure. When at least one of R's is, for example, an alkyl group, a metal such as a polymer of a tin-carbon bond chain is not formed, resulting in large hysteresis loss, which is not preferable.

In the method of the present invention, the amount of the organometallic compound represented by the structural formula MR ₄ added to the polymerization active terminal lithium is not particularly limited.

When an organometallic compound is used with respect to the polymerization active terminal lithium, the metal / lithium molar equivalent ratio is such that the polymerization activity, the content of the metal-carbon bond chain-containing polymer in the total polymer and the molecular weight of the polymer. Etc. have a great influence on.

When the molar equivalent ratio becomes large, when a conventional tin tetrachloride compound is used as the coupling agent,
It is well known that when the molar equivalent ratio of tin compound / lithium exceeds 0.25, the polymerization activity is completely lost. However, in the present invention, the reaction mechanism is different.
If it exceeds the above range, the polymerization activity becomes small, but the polymer has sufficient activity, and the obtained polymer has a large content of the above-mentioned metal-carbon bond chain-containing polymer and a small molecular weight. This tendency is promoted as the molar equivalent ratio is further increased.

When this molar equivalent ratio becomes smaller, the opposite tendency, that is, the polymerization activity becomes larger and the content of the metal-carbon bond chain-containing polymer becomes smaller, that is, the ratio of the polymer not containing the bond chain becomes smaller. The molecular weight also increases.

Therefore, by selecting the above molar equivalent ratio, a polymer suitable for the intended use can be obtained arbitrarily and easily.

The proportion of the high molecular weight polymer containing tin-carbon bond chains to the polymer not containing metals such as tin-carbon bond chains in the total polymer is above a certain level, for example 50.
It can be said that the polymer has a small hysteresis loss only when it is at least%, but the larger this ratio is, the smaller the hysteresis loss is, which is preferable. In the present invention, this ratio can be considerably higher than in the conventional method. The proportion of the high molecular weight polymer depends on the proportion of the lithium and the organometallic compound as described above, and by selecting the addition amount of the organometallic compound to the lithium at the polymerization active terminal, a polymer having a small hysteresis loss can be obtained. It is easily obtained and the object of the present invention is achieved. On the other hand, when the molar equivalent ratio is too small, for example, 0.3 or less, this ratio becomes too small and the obtained polymer has a large hysteresis loss, which is not preferable.

In the present invention, the timing of adding the organometallic compound is an important factor. This addition is carried out in the polymerization system immediately after the initiation of the polymerization with the organolithium compound and before the completion thereof, preferably at a conversion chain growth time of 80%, more preferably 20%. From the viewpoint of satisfying the two effects of achieving the continuous polymerization method and obtaining a polymer having a small hysteresis loss,
The addition timing may be from immediately after the start of polymerization to before the end or until the conversion reaches 80%, but to further enhance the effect, a kind of coupling reaction is performed at the low viscosity stage after the start of polymerization. And coupling efficiency is good, and the deactivation of active terminal lithium is small for various reasons in the initial stage of polymerization, so that a metal, for example, a tin-carbon bond chain-containing high molecular weight polymer, that is, a polymer with a small hysteresis loss is efficient. The conversion rate is 20% immediately after the initiation of the polymerization because of the fact that it can be obtained and that the continuous polymerization method can be stably performed.
It is preferable to add the organometallic compound at the initial stage of the polymerization. If the organometallic compound is added before the start of polymerization, the desired polymer cannot be obtained, and if added after the end of polymerization, the characteristics of the continuous polymerization method of the present invention will be lost.

In the present invention, the molecular structure of the desired polymer (molecular weight, microstructure, in the case of a copolymer, in addition to this, the composition of the monomer unit, its composition distribution, etc.) depending on the improvement of the polymerization activity and / or the application The conventional additives used for this purpose, for example, Lewis bases such as ether compounds and tertiary amine compounds, can be added to the reaction system in order to adjust the above). Examples of the ether compound used include diethyl ether, dibutyl ether, tetrahydrofuran,
2-methoxytetrahydrofuran, 2-methoxymethyltetrahydrofuran, 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 can be mentioned. Further, as secondary amine compounds, triethylamine, tripropylamine, pyridine, N, N,
N ', N'-tetramethylethylenediamine, N, N,
Examples thereof include N ', N'-tetraethylethylenediamine and N-methylmorpholine. Ether compounds and third
The amount of the primary amine compound used is 0.05 to 1000 mol per mol of the organic lithium compound.

The polymerization temperature is usually from -20 ° C to 150 ° C.
And preferably 0 ° C to 120 ° C.

The monomer concentration in the solvent is usually 5
˜50 wt%, preferably 10-35 wt%. 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
-50% by weight, preferably 5-40% 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 which is essentially sufficient to maintain the liquid phase. Also,
It is preferable to exclude substances interfering with the catalytic action from all of 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 dried on a hot roll or under reduced pressure to obtain the polymer. be able to. 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 metal such as a high molecular weight polymer having a tin-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 metal contained therein, for example, a high molecular weight polymer having a tin-carbon bond chain can be arbitrarily controlled in terms of molecular weight depending on the intended use. For example, the number average molecular weight of a branched polymer bonded to tin is 5 × 10 ^{4 to} 150 × 10 ^4.
Often the most valuable are useful.

Taking polybutadiene or a butadiene-styrene copolymer as an example, the microstructure of the butadiene part (cis-1,4, trans-1,4, vinyl), butadiene / styrene for the 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, for example, may be used alone or in a blend with a natural rubber or a synthetic rubber, if necessary, oil-extended, and then added with a usual compounding agent for vulcanized rubber and vulcanized. Used for anti-vibration rubber, belts, hoses and other industrial products, including tires.

[0041]

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. Room temperature resilience was used as an index of hysteresis loss. The larger the resilience, the smaller the hysteresis loss. JI for tensile properties and resilience
It was measured according to SK6301. The Mooney viscosity was measured by an ordinary method at 100 ° C. using an L rotor.

The tin-bonded branched polymer was prepared by dissolving 1 g of the whole polymer in 10 ml of toluene and adding concentrated hydrochloric acid 0.2
After adding ml, the mixture was stirred for 20 minutes, then precipitated in methanol and purified. This is based on the principle that the coupling portion of the polymer coupled with tin is cleaved by the treatment with hydrochloric acid.

The number average molecular weight (Mn) of all polymers and branched polymers was measured by gel permeation chromatography (GPC), and the differential refractive index (R
I) and the UV absorptivity (U.V.) of 254 nm were used, and the conversion was carried out in terms of polystyrene using monodisperse polystyrene as a standard.

The microstructure of the butadiene portion of the styrene-butadiene copolymer is determined by the infrared method (Morero method: DM
orero, Chim. e. Ind. , Vol. 41,
758 (1959)). The bound styrene content was determined from an infrared calibration curve based on the absorption of a phenyl group at 699 cm ^-1 .

There are various methods for measuring the concentration of the lithium at the polymerization active terminal used for calculating the molar equivalent ratio of the organotin 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 being sufficiently purified in advance, but in the ordinary polymerization, some of the initiator organolithium is water, carbon dioxide, etc. in the polymerization system. It is deactivated by 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 thus the polymerization was theoretically performed. It is known that the number average molecular weight (Mn) of a polymer holds as the following formula 1 (Takayuki Otsu, Experimental method of polymer synthesis, p212, Kagaku Dojin).

Formula 1 Mn = (number of moles of monomer / number of moles of organolithium initiator)
× Monomer molecular weight It has been found that the formula 1 is substantially valid also in the polymerization experiment carried out in the present invention, and the concentration of the organolithium is assumed to be the formula 2 at a certain ratio due to impurities.

Formula 2 Active polymerization terminal lithium concentration = Effective organolithium initiator mole number = Mole number of organolithium initiator charged at the time of initiation of polymerization × Organolithium residual rate Using the same reactor, the same lot of solvent and polymerization monomer It is clear that the assumption of the equation 2 holds when the above equation is used, and this equation is objectively used both industrially and empirically. Therefore, a preliminary experiment was conducted before carrying out this series of examinations, and
The residual rate of organolithium determined by using was determined to be 68%. Therefore, the concentration of active polymerization terminal lithium was 68% of the number of moles of the organolithium initiator charged in the polymerization initiator.

Example 1 1500 g of cyclohexane and 200 g of 1,3-butadiene were placed in a 5 l reactor equipped with a stirrer.
g, 50 g of styrene and 0.80 g of tetrahydrofuran were charged, and the temperature in the reaction vessel was adjusted to 60 ° C., then n-
Butyllithium (0.14 g) was added to initiate polymerization.

Immediately after the polymerization was initiated by charging n-butyllithium, 0.49 g of tetraallyl tin (manufactured by Aldrich Chemical Co.) was added. Then further polymerize 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 dried on a hot roll at 100 ° C. to obtain a rubbery polymer. The properties of the polymer are shown in Table 1.

The polymer had a composition of 25 according to the formulation shown in Table 3.
After kneading and blending with a 0 cc Labo Plastomill and a 3-inch roll, vulcanization was performed at 145 ° C. for 35 minutes. The physical properties of the vulcanized product are shown in Table 2.

[Examples 2 to 3] Polymerization was carried out in the same manner as in Example 1 except that 0.85 g of tetrabenzyl tin and 0.74 g of tetraphenyl tin (manufactured by Aldrich Chemical Co.) were added in Examples 2 and 3, respectively. went. Tetrabenzyltin was used after distilling a reaction product of tin tetrachloride with benzylmagnesium chloride (manufactured by Aldrich Chemical Co.) in diethyl ether under reduced pressure (mp = 4).
2-43 ° C). The properties of the polymer and the vulcanized physical properties of the polymer are shown in Tables 1 and 2.

Example 4 30.9 g of styrene was polymerized with 1.0 g of n-butyllithium in a hydrocarbon solvent as an initiator to polymerize a polystyrene polymer having a styryl-lithium polymer terminal having a molecular weight of 2000, and tetrachlorinated. Tin 1.
Tetrapolystyryl tin (polystyrene chain-tin bond structure was benzyl type) was obtained by a coupling reaction with 01 g. The polymer thus obtained was thoroughly purified and dried, and then 14.02 g of the polymer dissolved in 100 ml of benzene was added as an additive immediately after the initiation of polymerization, and the same procedure as in Example 1 was carried out. .. The properties of the polymer and the vulcanized physical properties of the polymer are shown in Tables 1 and 2.

Example 5 84.4 g of butadiene was polymerized with 0.5 g of n-butyllithium in a hydrocarbon solvent as an initiator to polymerize a polybutadiene polymer having a butadienyl-lithium polymer terminal having a molecular weight of about 10,000, and Tetrapolybutadienyl tin (polybutadiene chain and tin bond structure is allyl type) was obtained by a coupling reaction with 0.51 g of tin chloride. After sufficiently purifying and drying the polymer thus obtained, cyclohexane 4
The same procedure as in Example 1 was repeated except that 75.34 g of the polymer dissolved in 00 ml was added as an additive immediately after the initiation of polymerization. Table 1 shows the properties of the polymer and the physical properties of the vulcanized polymer.
And shown in Table 2.

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

Comparative Examples 2 to 4 In Comparative Examples 2, 3 and 4, 0.55 of diallyldibutyltin was added after the initiation of polymerization.
g, 0.58 g of allyltributyltin (manufactured by Aldrich Kelcal) and 0.60 g of tetrabutyltin (manufactured by Aldrich Chemical) were added, and polymerization was carried out in the same manner as in Example 1. Diallyldibutyltin was used after distilling a reaction product of dibutyltin chloride and allylmagnesium bromide (manufactured by Aldrich) in diethyl ether under reduced pressure (bp 93 ° C./0.1 mmH).
g). Table 1 shows the properties of the polymer and the physical properties of the vulcanized polymer.
And shown in Table 2.

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

[Table 3]

As shown in Table 1, in the examples of the present invention, the polymerization was carried out by adding an organotin compound as a coupling agent at the initial stage of the polymerization of butadiene-styrene copolymerization. Despite the large equivalent ratio, the polymerization proceeded and the obtained polymer was butadiene-containing a substantial amount of a high-molecular weight tin-carbon bonded chain-containing polymer.
It was a high molecular weight rubbery copolymer having a styrene random structure. The inclusion of a substantial amount of the tin-carbon bonded polymer is apparent by comparing the molecular weights of the total polymer and the branched polymer. As can be seen from the comparison with the comparative example, the vulcanized product of this polymer exhibited a well-balanced physical property with a large resilience at 25 ° C., that is, a small hysteresis loss, without impairing the fracture characteristics.

As described above, even though the organotin compound is added as a kind of coupling agent at the initial stage of the polymerization, the polymerization proceeds stoichiometrically as in the ordinary living polymerization, and the high molecular weight is useful. The fact that a polymer having various tin-carbon bond chains was obtained clearly shows that a continuous polymerization method was possible.

In Comparative Example 1, no coupling agent was added, and the obtained vulcanized product had a small resilience, that is, a large hysteresis loss and a poor exothermic property. This is a phenomenon that is contrasted with the fact that the hysteresis loss of the tin-carbon bond chain-containing polymer is small, as shown in the examples.

Comparative Examples 2 to 4 are systems in which an organotin compound in which some or all of the allyl groups of tetraallyltin used in Example 1 are changed to butyl groups is added. The obtained polymer did not contain tin at all (confirmed by UV), and the molecular weight of the polymer before and after the treatment with hydrochloric acid was not changed at all. That is, there was no branched polymer attached to tin. Therefore, the physical properties of the vulcanized product are not desirable because of its low resilience. This result is exactly the same as Comparative Example 1 using no organotin compound, which shows that the organotin compound having such a structure has no effect.

[0066]

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

Claims (1)

[Claims] 1. A method for producing a polymer by polymerizing a conjugated diene and / or a vinyl aromatic hydrocarbon by using an organolithium compound as an initiator in a hydrocarbon solvent, the method comprising the structural formula MR ₄ (M: tin, germanium and Immediately after the initiation of the polymerization, an organometallic compound represented by a metal selected from lead and an R: M bond having an allyl structure, a benzyl structure or a phenyl structure and represented by the same or different molecular structure group) From the end to the end of the polymerization chain growth, the method for producing a polymer is characterized in that the polymerization reaction is carried out by adding to the polymerization system.