JPH11209439A - Production of polymer, polymer, and rubber composition containing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent process for producing a multi-branched polymer and to provide a rubber composition containing the polymer and having excellent breaking characteristics and processability. SOLUTION: There are provided a process for producing a polymer which comprises: polymerizing or copolymerizing a conjugated diene in the presence of an initiator being an organolithium compound in a hydrocarbon solvent and allowing to act on the active terminals of the polymer a poly(meth)acrylic ester represented by the formula (X is a polyvalent alkyl ether group having at least two terminal ether groups; R is hydrogen or methyl; and n is the number of the etheric oxygen atoms of X, bonded to the carbonyl groups of the methacrylic groups) to produce a highly branched polymer and a rubber composition containing at least 30 pts.wt., per 100 pts.wt. rubber component, above polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The polymer obtained by the process for producing a polymer of the present invention has a low bulk viscosity despite having a high molecular weight, so that a good breaking property and workability can be highly compatible with each other. A rubber composition can be obtained. Further, when this rubber composition is used for a tire for a passenger car, a good grip characteristic can be obtained due to a high loss characteristic.

[0002]

2. Description of the Related Art Various technical means have been developed as means for improving the breaking characteristics and abrasion resistance of a compounded rubber composition. Among them, it is generally known that increasing the molecular weight of the polymer of the rubber component used in the rubber composition is particularly effective as a means for improving the breaking characteristics. However, it is known that when a polymer having such a high molecular weight is used for a rubber composition, the viscosity of the composition before vulcanization is significantly increased, and the processability is significantly deteriorated.

In order to improve the relationship between the molecular weight and the workability, attempts have recently been made to introduce a branched structure into a polymer. It is known that, when a polymer has a branched structure, the entanglement between polymer molecules becomes considerably small, and thus the viscosity in such a bulk state becomes considerably small. Methods for synthesizing such star-branched polymers include, for example, Headjichristidies et.al and acrolecucu.
les 13, 191 (1980), Advance in polymer sience,
In P. Rempp et.al, 86 p.161, Springer-Verg (1988), the following method is known as a main method. (1) A method using a polyvalent organic lithium compound as a polymerization initiator. (2) A method of obtaining branching by using an alkyllithium compound as an initiator and a polyvalent metal halide compound, an organic halogen compound or an organic phosphorus compound as a coupling agent. (3) A method in which styrene is copolymerized with a polyvalent vinyl compound, particularly divinylbenzene, using an alkyllithium compound as an initiator.

[0004] However, it has become clear that these conventional methods have various problems. For example, in the method (1) using a polyvalent organolithium compound as an initiator, it is generally difficult to synthesize such a polyvalent organolithium compound, and it is difficult to stabilize the synthesized polyvalent lithium compound. Some have poor sex,
Moreover, such compounds often have low solubility in hydrocarbons. Thus, there are practically considerable problems.

As a method of using the polyvalent coupling agent of the above (2), a tetravalent coupling agent such as SiCl ₄ can be obtained relatively easily, but a polyvalent coupling agent having a higher valence can be obtained. In the method using a metal halide, the synthesis of the coupling agent itself is difficult in that a multi-step reaction must be used. In the method using an organic halogen compound, it is known that when such a reaction is performed in a hydrocarbon solvent, the transmetallation reaction proceeds as a side reaction, and the branching efficiency of the product is not sufficient. Further, in the method using an organic phosphorus compound,
There is a practical problem because the high toxicity that phosphorus compounds often have and the resulting polymer itself becomes unstable.

Further, when divinylbenzene, for example, is used as the polyvalent vinyl compound (3), the dispersion of the polymerization is large, and the degree of branching and reproducibility of the obtained polymer are poor.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and an object of the present invention is to provide a method for easily producing a hyperbranched polymer and a polymer obtained in this manner. It is an object of the present invention to provide a rubber composition having excellent fracture characteristics and processability at the same time.

[0008]

Means for Solving the Problems The present inventors have focused on the coupling agent, and as a result of intensive studies, as a result, various methods in the synthesis of a multi-branched polymer which were difficult to sufficiently solve by the above-mentioned known methods have been described. The present inventors have found that the above object can be achieved by the following means, for example, by using a novel polyvalent coupling agent (meth) acrylate (general term for acrylate and methacrylate), and completed the present invention. I came to.

That is, (1) In the method for producing a polymer of the present invention, after a conjugated diene monomer is polymerized or copolymerized in a hydrocarbon solvent using an organolithium compound as an initiator, A highly branched polymer is obtained by reacting an active terminal with a polyvalent (meth) acrylate represented by the following general formula. General formula

[0010]

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Wherein X represents a polyvalent alkyl ether group having two or more terminal ether groups, R represents a hydrogen atom or a methyl group, and n represents a carbonyl group of a (meth) acryl group in the X group. (2) In the above (1), the polyvalent (meth) acrylate is ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, It is preferably one compound selected from the group consisting of glycerin tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, neopentyl glycol di (meth) acrylate and dipentaerythritol hexa (meth) acrylate. (3) In the above item (1), the polymer is preferably a copolymer of a conjugated diene monomer and a vinyl aromatic monomer. (4) In the above item (3), the conjugated diene monomer and the vinyl aromatic monomer are preferably butadiene and styrene, respectively. (5) The polymer of the present invention is obtained by the production method described in the above (1), (2), (3) or (4). (6) In the above item (5), the molecular weight of the polymer is 40.
Preferably it is ~ 2.5 million. (7) The rubber composition of the present invention is characterized in that the polymer described in the above item (5) or (6) is contained in an amount of 30 parts by weight or more per 100 parts by weight of the rubber component.

In the present invention, the high reactivity of the (meth) acrylate compound with the anionic polymerized terminal lithium of the diene monomer, particularly, The present inventors arrived at the present invention as a result of investigating that such a compound has both homopolymerization of itself and terminal coupling addition reactivity with a conjugated diene-based polymer.

In the present invention, a highly branched polymer, which has been difficult to synthesize, can be converted into a polyvalent (meth) acrylate without using a conventional expensive polyfunctional coupling agent which is difficult to synthesize. It is characterized in that it is used as a coupling agent.

Here, the formation mechanism of the polyvalent coupling agent and the highly branched polymer will be described below by way of example.

For the purpose of explanation, polybutadiene obtained by polymerization using butadiene as a conjugated diene monomer and organic lithium as an initiator is used as PBD, and lithium polybutadiene having an active terminal anion bonded to lithium is referred to as PBDLi (A).
Further, it is assumed that the mono (meth) acrylate as a model of the elementary reaction is methyl acrylate (B) and the polyvalent (meth) acrylate used in the present invention is ethylene glycol diacrylate (E). I. Addition reaction of lithium polybutadiene with methyl acrylate (elementary reaction X) Formula 1

[0016]

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II. Polymerization reaction of methyl acrylate with adduct (C) (elementary reaction Y) Formula 2

[0018]

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III. Addition reaction of lithium polybutadiene with ethylene glycol acrylate Formula 3

[0020]

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IV. Polymerization reaction of ethylene glycol diacrylate with adduct (F) Formula 4

[0022]

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V. Addition reaction of lithium polybutadiene with polyvalent coupling agent Formula 5

[0024]

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It is known that (meth) acryl groups have high reactivity with organolithium compounds. The reaction of a mono (meth) acryl group is generally carried out by the elementary reaction X of the above I.
It is known that this occurs as shown in the formula 1 of the above formula and the elementary reaction Y of the above II. That is, the elementary reaction X indicates an addition reaction of a double bond between lithium polybutadiene (A) and methyl acrylate (B), and an adduct (C) is obtained. The elementary reaction Y represents a polymerization reaction of the double bond of the ester (B) with the lithium enolate of the adduct (C), and the polymer (D)
Is obtained. The present invention focuses on the two elemental reactivities (addition reaction and polymerization reaction) of a mono (meth) acryl group, and uses a polyvalent (meth) acrylate to form a polyvalent coupling with a known mono (meth) acrylate. The present invention has been completed by obtaining a new agent and obtaining a new finding that a hyperbranched polymer can be obtained.

In the present invention, when ethylene glycol diacrylate (E) is used as an example of the polyvalent (meth) acrylate as shown in the above formula (3), it is subjected to an addition reaction with lithium polybutadiene (A). , Adduct (F) is obtained. Next, as shown in Formula 4 of IV, the polyvalent coupling agent (G) is obtained by a polymerization reaction of one double bond of the diacrylate (E) with the lithium enolate of the adduct (F). Finally, as shown in Formula 5 of V, a polybranched polybutadiene polymer (H) can be produced by adding lithium polybutadiene (A) to a plurality of acrylic groups of the polyvalent coupling agent (G).

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the rubber composition of the present invention is obtained by polymerizing or copolymerizing a conjugated diene monomer in a hydrocarbon solvent using an organic lithium compound as an initiator. A conjugated diene-based polymer having an atomic group represented by the general formula at a polymer chain terminal of a polymer or a copolymer obtained by reacting a polymer active terminal and a polyvalent acrylate represented by the above general formula. Including. This polymer must be contained in an amount of at least 30 parts by weight, preferably at least 50 parts by weight, per 100 parts by weight of the rubber component. If the amount of the conjugated diene polymer is less than 30 parts by weight of the total rubber component, the effect of the present invention cannot be sufficiently obtained. All of the rubber components may be the conjugated diene-based polymer of the present invention.

As the rubber component used in the present invention,
Examples of those used with the conjugated diene-based polymer include natural rubber, and a diene-based synthetic rubber,
Diene-based synthetic rubbers include styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), butyl rubber (IIR), ethylene-
Propylene copolymer rubber, and mixtures thereof, and the like. A part thereof may have a branched structure by using a polyfunctional modifier, for example, a modifier such as tin tetrachloride.

The polymer used in the present invention is preferably a copolymer of a conjugated diene monomer and a monovinyl aromatic monomer.

The conjugated diene monomer used in the present invention includes, for example, 1,3-butadiene, isoprene,
3-pentadiene, 2,3-dimethylbutadiene, 2-
Examples thereof include phenyl-1,3-butadiene and 1,3-hexadiene. These may be used alone or in combination of two or more. Among them, 1,
3-butadiene.

The vinyl aromatic monomer used for copolymerization with the conjugated diene monomer includes styrene, α-
Methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene,
-Cyclohexylstyrene, 2,4,6-trimethylstyrene and the like. Among them, styrene is preferred.

Further, when copolymerization is carried out using a conjugated diene monomer and a vinyl aromatic monomer, it is particularly preferable to use 1,3-butadiene and styrene, respectively.

Examples of the organolithium compound as an initiator used in the polymerization include a hydrocarbon compound of lithium metal or a complex with a polar compound. . Preferably, 2 to 20
It is a lithium compound having three carbon atoms. For example,
Ethyl lithium, n-propyl lithium, i-propyl lithium, n-butyl lithium, sec-butyl lithium, t-octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butyl-phenyl lithium, 4-phenyl-butyllithium, cyclohexyllithium, 4-cyclopentyllithium and the like.

The amount of the initiator used is usually in the range of 0.2 to 20 mmol per 100 g of the monomer.

The polymers of the present invention are run in solvents that do not destroy the organolithium initiator, such as hydrocarbon solvents. Suitable hydrocarbon solvents are selected from aliphatic hydrocarbons, aromatic hydrocarbons, and alicyclic hydrocarbons.
With propane, n-butane, i-butane, n-pentane, i-pentane, n-hexane, cyclohexane, propene, 1-butene, i-butene, trans-2
-Butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene and the like are preferred. These solvents can be used as a mixture of two or more kinds.

The concentration of the monomer in the solvent is usually from 5 to
It is 50% by weight, preferably 10 to 30% by weight. In the case of copolymerization of a conjugated diene and a vinyl aromatic hydrocarbon, the content of the vinyl aromatic hydrocarbon in the charged monomer mixture is 3 to 5%.
0% by weight, preferably 5 to 45% by weight.

In the present invention, a known randomizer can be used for anionic polymerization of the conjugated diene monomer. Here, the randomizer means control of the microstructure of the conjugated diene polymer, for example, increase of 1,2 bond of butadiene portion of butadiene polymer or butadiene-styrene copolymer, increase of 3,4 bond of isoprene polymer, and the like. It is a compound having an action of controlling the composition distribution of monomer units of the conjugated diene-vinyl aromatic hydrocarbon copolymer, for example, randomizing butadiene units and styrene units of a butadiene-styrene copolymer. The randomizer of the present invention is not particularly limited, but includes all commonly used randomizers. These include, for example, dimethoxybenzene, tetrahydrofuran, ditetrahydrofurylpropane, dimexiethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, triethylamine, pyridine, N-methylmorpholine, N, N, N'N'-terolamethylethylenediamine, 1,2- Examples thereof include ethers such as dipiperidinoethane and tertiary amines. Further, potassium salts such as potassium-t-amylate and potassium-t-butoxide, and sodium salts such as sodium-t-amylate can also be used.

The amount of the randomizer used is in the range of 0.01 to 1000 molar equivalents per 1 molar equivalent of the organic lithium compound.

The polymerization of the conjugated diene polymer of the present invention is carried out by about-
The reaction can be performed at any temperature within the range of 80 to 150 ° C, but a temperature of -20 to 100 ° C is preferable. Although the polymerization reaction can be carried out under the generated pressure, it is usually desirable to operate at a pressure sufficient to keep the monomer substantially in a liquid phase. That is, the pressure will depend on the particular material being polymerized, the diluent used and the polymerization temperature, but higher pressures can be used if desired, and such pressures are maintained in the reactor with gases inert to the polymerization reaction. Is obtained by an appropriate method such as pressurization.

In general, it is preferred to remove water, oxygen, carbon dioxide and other catalyst poisons from all substances involved in the polymerization process, such as initiator components, solvents, monomers and the like.

In the polyvalent (meth) acrylate (coupling agent) used in the present invention, two or more (meth) acryl groups must be present in the molecule. When there is only one (meth) acryl group, the branching reaction does not proceed, and a branched polymer cannot be obtained. Further, it is desirable that there are four or more (meth) acryl groups.
In the method of the present invention, this proceeds by a method as shown in both the polymerization of the polyvalent (meth) acrylate and the addition reaction of the polymer terminal (exemplified by the above formula 4) and the polymer terminal (exemplified by the above formula 5). However, if the polymerization reaction of the polyvalent (meth) acrylate is not sufficient, the degree of branching of the obtained polymer may not be sufficient. There is no particular limitation as long as the number of (meth) acrylic groups is 2 or more, but generally, commercially available polyvalent (meth) acrylic acid derivatives have 8 or less (meth) acrylic groups. It is. Specific examples of the polyvalent (meth) acrylate in the present invention include, for example, ethylene glycol di (meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, triethylene glycol di (meth) acrylate,
Neopentyl glycol di (meth) acrylate; and the like.

As the reaction temperature of the polyvalent (meth) acrylic acid compound and the terminal lithium of the polymer exemplified in the above formula 3, the polymerization or copolymerization temperature of the conjugated diene monomer can be used as it is. Specifically, a preferable range is 30 ° C to 100 ° C. If the temperature is lower than 30 ° C., the viscosity of the polymer tends to increase too much.

The amount of the polyvalent (meth) acrylate used in the present invention is determined by the amount of (meth) acrylic acid per mole of lithium of the organolithium compound used in the polymerization or copolymerization of the conjugated diene monomer. Usually 0.5 to 10 in moles of the group
Mol, preferably 0.1 to 5 mol. 0.5
When the amount is less than 10 moles, the degree of branching of the obtained polymer is practically insufficient, and when the amount is 10 moles or more, polymerization ends are deactivated due to impurities contained in an excess polyvalent (meth) acrylate. In this case, the reaction efficiency cannot be sufficiently obtained.

The method of adding these polyvalent (meth) acrylates to the terminal of the polymer chain is generally carried out after the completion of the polymerization when such a modifier is used.

The analysis of the polymer chain terminal modifying group can be performed by a method using GPC. The molecular weight of the conjugated diene polymer in the present invention is from 400,000 to 2.5 million, preferably from 70 to 200, by a method using GPC described later.
If the molecular weight is less than 400,000, rubber properties such as breaking characteristics cannot be sufficiently obtained, and if it exceeds 2.5 million, workability is poor, and it is difficult to knead with the compounding agent.

The rubber composition of the present invention contains a filler, and any filler generally used for a rubber compounding agent can be used.

Examples of the carbon black to be used include carbon blacks such as FEF, SRF, HAF, ISAF, SAF and the like.
Carbon black having A) of 60 mg / g or more and dibutyl phthalate oil absorption (DBP) of 80 ml / 100 g or more is used. In particular, HAF, which has excellent wear resistance,
ISAF and SAF are preferred.

The amount of the carbon black is not particularly limited, but from the viewpoint of reinforcing properties and processability, the rubber component 10
With respect to 0 parts by weight, within the range of the filler, 0.1% by weight.
It is preferable to add 1 to 130 parts by weight of carbon black.

Examples of the silica used include, for example, wet silica (hydrous silicic acid) and dry silica (silicic anhydride). Among them, the effect of improving the breaking characteristics and the effect of achieving both wet gripping property and low rolling resistance are provided. Is most preferable.

Examples of the vulcanizing agent include sulfur and the like. The amount of these used is preferably 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, as the sulfur content relative to 100 parts by weight of the rubber component. It is. If the amount is less than 0.1 part by weight, the breaking strength, abrasion resistance, and low heat build-up of the vulcanized rubber are reduced.

The process oil that can be used in the polymer composition of the present invention includes, for example, paraffinic, naphthenic, and aromatic oils. For applications that emphasize tensile strength and abrasion resistance, aromatics are used, and for applications that emphasize hysteresis loss and low-temperature characteristics, naphthenes or paraffins are used. The amount used is based on 100 parts by weight of the rubber component. The amount is preferably from 0 to 100 parts by weight, and if it exceeds 100 parts by weight, the tensile strength and low heat build-up of the vulcanized rubber tend to deteriorate.

The vulcanization accelerator that can be used in the present invention is not particularly limited, but is preferably M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), or CZ (N-cyclohexyl-2). Benzothiazylsulfenamide) and other thiazole-based DPGs
(Diphenylguanidine) and other guadinine-based vulcanization accelerators.
The amount is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 3 parts by weight, based on 0 parts by weight.

In the present invention, in addition to these, additives such as an antioxidant, zinc oxide, stearic acid, an ozone deterioration inhibitor and the like which are usually used in the rubber industry can be blended.

The rubber composition of the present invention is obtained by kneading using a kneading machine such as a roll or an internal mixer. After molding, vulcanization is performed to obtain a tire tread, an undertread, a carcass and a side. It can be used for tires such as walls and beads, as well as anti-vibration rubber, belts, hoses and other industrial products.
Particularly, it is suitably used as a rubber for a tire tread.

[0055]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention.

In the examples, parts and% mean parts by weight and% by weight, respectively, unless otherwise specified. Various measurements were made according to the following methods. (1) Physical Properties of Copolymer The molecular weight (MW) of the copolymer was measured by gel permeation chromatography [GPC; HLC-8 manufactured by Tosoh Corporation]
020, column; Tosoh GMH-XL (two in series)]
And using a differential refractive index (RI) and monodisperse polystyrene as a standard in terms of polystyrene.

The Mooney viscosity of the copolymer was measured using a RLM-01 type tester manufactured by Toyo Seiki Co., Ltd. according to JIS K6300-
Measured according to 1994.

The microstructure of the butadiene portion of the copolymer was determined by an infrared method (Morello method).

The bound styrene content in the copolymer is 1H-
It was calculated from the integration ratio of the NMR spectrum. Polymer T
g was measured using a differential thermal analyzer (DSC) model 7 manufactured by Perkin Elmer Co., Ltd. after cooling to -100 ° C and then heating at 10 ° C / min.

Coupling efficiency was determined using the area ratio of high molecular weight fragments obtained by GPC analysis. (2) Physical Properties of Rubber Composition Fracture characteristics (Tb, Eb) and tensile stress at 300% elongation (M300) were measured at room temperature in accordance with JIS K6301-1995.

The hardness was measured using a spring type hardness tester type A in accordance with JIS K6301-1995.

Experiments were carried out using dried and purified raw materials used in the polymerization unless otherwise specified. (Polymerization Example 1) 300 g of cyclohexane and 1,3-
32.5 g of butadiene monomer, 17.5 styrene monomer
g, 0.4 mmol of ditetrahydrofurylpropane, and 1.0 mmol of n-butyllithium (BuLi) was added thereto.
After adding 1, polymerization was carried out at 50 ° C. for 2 hours. The polymerization system was uniform and transparent without any precipitation from the start to the end of the polymerization. The polymerization conversion was almost 100%. To this reaction system was added 0.25 mmol of dipentaerythritol hexaacrylate as a coupling agent, and 30
A minute coupling reaction was performed. Thereafter, the solvent was removed by a conventional method, followed by drying to obtain a polymer A. The results of the analysis of this polymer are shown in Table 1.

As a result of GPC analysis, when comparing the molecular weight of the fragment after coupling with the unreacted fragment of this polymer with the coupling agent,
It is about 8 times, and it is considered from this result that a polymer having at least 8 branches or more was formed in this coupling reaction. (Polymerization Examples 2 to 15) Polymer B of Polymerization Examples 2 to 15
ＯO was produced in the same manner as in Polymerization Example 1 according to Tables 1 to 3, except that the amount of the initiator and the type and amount of the coupling agent were changed. (Comparative Polymerization Example 1) 300 g of cyclohexane, 1,3-
35 g of a butadiene monomer, 15 g of a styrene monomer and 0.2 mmol of ditetrahydrofurylpropane were injected, and 0.5 mmol of n-butyllithium (BuLi) was added thereto, followed by polymerization at 50 ° C. for 2 hours. The polymerization system was uniform and transparent without any precipitation from the start to the end of the polymerization. The polymerization conversion was almost 100%. After 0.1 mmol of silicon tetrachloride was added to the reaction system and a coupling reaction was carried out for 30 minutes, 0.1 ml of isopropanol was added to terminate the polymerization. Thereafter, the solvent was removed according to a conventional method, followed by drying to obtain a polymer P. The polymerization conversion was almost 100%. The results of analysis of this polymer are shown in Table 4. (Polymerization Comparative Examples 2 to 4) Polymers Q to S of Polymerization Comparative Examples 2 to 4
Was prepared in the same manner as in Comparative Example 1, except that the amount of the initiator and the amount of the coupling agent were changed according to Table 4.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

[0067]

[Table 4]

(Compounding Examples 1 to 4, and Comparative Comparative Example 1) Using the polymers obtained as described above, rubber compositions were prepared according to the formulations shown in Table 5, and their physical properties were evaluated. Table 6 shows the results.

[0069]

[Table 5]

[0070]

[Table 6]

As shown in Tables 1 to 4 and 6, the polymer synthesized by the method of the present invention was different from the polymer of the comparative example.
It can be seen that even those having the same molecular weight show a low Mooney viscosity. This is considered to be because the polymer according to the present invention has a high degree of branching, and has a small entanglement with a polymer having a normal degree of branching having the same molecular weight.

The blending examples 1 to 4 using the conjugated diene polymer of the present invention have a lower blending Mooney viscosity than the comparative example having the same molecular weight, and are particularly excellent in workability. Is evident. In addition, when rubber compositions having the same Mooney viscosity are compared, it can be understood that the rubber composition having excellent tensile strength can be obtained by exhibiting excellent tensile strength, and the effect of the present invention can be understood.

[0073]

As described above, in the present invention, a hyperbranched polymer can be easily produced, and a rubber composition using the obtained polymer has improved fracture characteristics and good processability. It has an excellent effect of being highly compatible.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // C08F 4/48 C08F 4/48

Claims (7)

[Claims] 1. A conjugated diene monomer is polymerized or copolymerized in a hydrocarbon solvent using an organolithium compound as an initiator, and then the active terminal of the polymer and a polyvalent compound represented by the following general formula: By reacting (meth) acrylic acid ester,
A method for producing a polymer, characterized in that a highly branched polymer is obtained. General formula (Wherein, X represents a polyvalent alkyl ether group having two or more terminal ether groups, R represents a hydrogen atom or a methyl group, and n binds to a carbonyl group of a (meth) acryl group in the X group. , Represents the number of ether oxygens.) 2. The polyvalent (meth) acrylic ester is ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, glycerin tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, neopentyl. The method for producing a polymer according to claim 1, wherein the compound is one compound selected from the group consisting of glycol di (meth) acrylate and dipentaerythritol hexa (meth) acrylate. 3. The method for producing a polymer according to claim 1, wherein the polymer is a copolymer of a conjugated diene monomer and a vinyl aromatic monomer. 4. The method according to claim 3, wherein the conjugated diene monomer and the vinyl aromatic monomer are butadiene and styrene, respectively. 5. A polymer obtained by the production method according to claim 1, 2, 3, or 4. 6. The polymer according to claim 5, wherein the molecular weight of the polymer is 400,000 to 2.5 million. 7. A rubber composition comprising the polymer according to claim 5 or more in an amount of 30 parts by weight or more per 100 parts by weight of the rubber component.