JP2015054866A - Production method of zinc terminal modified-polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a zinc terminal modified-polymer capable of enhancing the dispersibility of silica used as a compounding agent of a pneumatic tire composition for an automobile.SOLUTION: A production method of a zinc terminal modified-polymer comprises a step of performing polymerization reaction of aromatic vinyl monomers, conjugated diene monomers, or both of them, in the presence of an anionic polymerization initiator, ane then adding a zinc halide compound or zinc salt of unsaturated monocarboxylic acid thereto so as to stop the polymerization reaction. The zinc terminal modified-polymer can be also produced by adding a zinc halide compound or zinc salt of unsaturated monocarboxylic acid so as to stop the polymerization reaction, and then adding lower alcohol having the carbon number of 1 to 4.

Description

  The present invention relates to a method for producing a terminal-modified polymer. More specifically, the present invention relates to a method for producing a terminal-modified polymer that improves the dispersibility of silica used as a compounding agent for an automotive pneumatic tire composition.

  As various performances required for pneumatic tires for automobiles, reduction of rolling resistance, stability on wet road surfaces, and the like are required. As a method for achieving both of these properties, silica is compounded as a reinforcing filler in a tire rubber composition. However, even if silica is added to the rubber composition for tires, the dispersibility of silica in the composition is low, and even if a large amount of silica can be added, there is a problem that the effect cannot be sufficiently exhibited. It is done.

  Patent Document 1 discloses an elastomer / filling that is useful as a tire component and the like, in which a reinforcing filler is uniformly dispersed by forming the reinforcing filler in the elastomer host material in situ from its precursor. A method for producing a composite material is described, and in order to composite silica as a filler, a reaction from a filler precursor is required.

  In Patent Document 2, a filler precursor, a condensation reaction accelerator and an elastomer host (A) or (B) are blended in a closed mixer to start a condensation reaction of the filler precursor, and an elastomer host (A) And optionally for the elastomer host (B), the organosilane material and the filler / filler precursor are added and reacted in a closed mixer before the condensation reaction is complete and the resulting elastomer / filler composite is recovered. A method for producing an elastomer / filler composite is described. And it is stated that this composite material is used as an active ingredient of a rubber composition for tires, particularly a rubber composition for tire treads.

Here, the elastomer host (A) is a homopolymer of a conjugated diene or a copolymer of a conjugated diene and a vinyl aromatic monomer, and the elastomer host (B) is at least one alkoxy metal terminal functionalized diene-based elastomer. This diene-based elastomer has a general formula
Elastomer-X- (OR) n
Elastomer: Conjugated diene homopolymer or conjugated diene and vinyl
Copolymer with aromatic monomer
X: Metal made of Si, Ti, Al or B
R: alkyl group of C ₁ -C ₄
n: 3 for Si and Ti, 2 for Al and B
(Claim 5, paragraph [0014]).

  However, in each example of Patent Document 2, only the description that styrene and 1,3-butadiene are copolymerized in an organic solvent in the presence of a lithium-based catalyst and then the elastomer is recovered is used as an elastomer end group. There is no description regarding a method for producing a terminal-modified polymer into which an X- (OR) n group is introduced.

  In Patent Document 3, a polymer having a terminal diester group is produced by reacting a diester compound such as ditertiary alkyl maleate with an art complex composed of a living polymer and a compound containing a typical metal element such as aluminum. Then, a method for producing a terminal acid anhydride group-containing polymer in which the diester group is converted into an acid anhydride group is described.

The art complex used here will be described. First, when anionic polymerization of styrene is performed using butyllithium, the end of the polymer becomes ~ C ^- Li ⁺ unless the reaction is stopped. The -C ^- Li ⁺ in Li ⁺ belong to hard acid referred to HSAB theory, therefore of the pair -C ^- is as shown a high reactivity. In general, in this state, its high ~C showing reactivity (nucleophilic) ^- is a result of the attack to the carbonyl carbon, the introduction of the acid anhydride group is difficult, it is converted Therefore the hard acid soft acid Is done.

In this patent document, by using a trialkyl aluminum compound not containing leaving group as its method, i.e. -C ^- the Li ⁺ -C ^- by (AlR ₃ Li) ⁺ to changing, that allowed to lower the reactivity The technique is taken.

JP 2000-273191 A JP 2000-143881 A JP 2007-084711 A JP 2005-272580 A

  The objective of this invention is providing the manufacturing method of the terminal modified polymer which improves the dispersibility of the silica used as a compounding agent etc. of the composition for automotive pneumatic tires.

  The object of the present invention is to polymerize a vinyl aromatic monomer, a conjugated diene monomer, or both in the presence of an anionic polymerization initiator, and then add a zinc halide compound or an unsaturated monocarboxylic acid zinc salt thereto. It is achieved by a method of adding and stopping the polymerization reaction to produce a terminal zinc-modified polymer. Alternatively, a terminal zinc-modified polymer can also be produced by adding a zinc halide or an unsaturated monocarboxylic acid zinc salt to stop the polymerization reaction and then adding a lower alcohol having 1 to 4 carbon atoms. it can.

  In the terminal zinc-modified polymer produced by the method of the present invention, the polymer can be easily obtained by using a zinc halide compound or an unsaturated monocarboxylic acid zinc salt as a polymerization reaction terminator, or by further alkoxylation. Groups derived from these compounds can be introduced at the ends.

  When the obtained terminal zinc-modified polymer is blended as a component in a rubber composition for a silica-blended pneumatic tire, the dispersibility of the silica blended in the rubber composition is improved, and the rolling resistance inherent in silica is improved. It is possible to satisfactorily satisfy the problem of both reduction and stability on wet road surfaces.

  The polymer whose end groups are modified is formed as a vinyl aromatic monomer, a conjugated diene monomer, or a polymer of both. Examples of the vinyl aromatic monomer include styrene, α-methylstyrene, p-methylstyrene, 2,4,6-trimethylstyrene, vinyltoluene, 1-vinylnaphthalene, and preferably styrene is used. Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 1,3-hexadiene, chloroprene, and preferably 1,3-butadiene or isoprene. Used. Both of these vinyl aromatic monomers and conjugated diene monomers can be used in combination, and preferably both styrene and 1,3-butadiene or isoprene are used. When both of these are used, the resulting polymer is generally a random copolymer, but it may be a block copolymer.

  The polymerization reaction is performed by an anionic polymerization method using an anionic polymerization initiator. As the anionic polymerization initiator, an organic lithium compound, preferably alkyl lithium or aryl lithium is used.

  Examples of the alkyl lithium include methyl lithium, ethyl lithium, propyl lithium, n-butyl lithium, secondary butyl lithium, tertiary butyl lithium, isobutyl lithium, hexyl lithium, octyl lithium, tetramethylene dilithium, and m-diisopropenylbenzene. Examples of the aryllithium include phenyllithium and tolyllithium. These may be used singly or in combination of two or more, and from the viewpoints of handleability and industrial economy, n-butyllithium, secondary butyllithium, and tertiary butyllithium are preferable. From the viewpoint of reactivity, n-butyl lithium and secondary butyl lithium are more preferable.

  These organolithium compounds are generally used in a proportion of about 0.0001 to 10 mol%, preferably about 0.0005 to 6 mol%, based on the amount of monomer (mixture) charged.

  In the polymerization reaction system, 2,2-ditetrahydrofurylpropane, N, N, N ′ used in a proportion of about 10 to 300 mol%, preferably about 40 to 200 mol%, relative to the molar amount of initiator used. , N′-tetramethylethylenediamine, diethyl ether, monoglyme, diglyme, dimethoxyethane, tetrahydrofuran and the like are used. These compounds act as a randomizer in an anion initiator and a growth species activator or copolymerization when a nonpolar solvent such as cyclohexane or methylcyclohexane is used in the polymerization reaction.

  The polymerization reaction is carried out using a hydrocarbon solvent such as cyclohexane, methylcyclohexane, toluene, tetrahydrofuran and the like at about -100 to 100 ° C, generally about 0 to 70 ° C for about 1 to 5 hours, and thereafter A zinc halide compound or an unsaturated monocarboxylic acid zinc salt is added to the polymerization reaction system to stop the polymerization reaction. The amount of zinc halide compound or unsaturated monocarboxylic acid zinc salt is an amount sufficient to introduce the end groups of the resulting polymer, for example about 33-1000, based on the molar amount of anionic polymerization initiator used. It is used in a proportion of mol%, preferably about 100 to 400 mol%.

As the zinc halide compound, zinc chloride, zinc bromide, zinc iodide or zinc fluoride is used, and zinc chloride ZnCl ₂ is preferably used. Further, as the unsaturated monocarboxylic acid zinc salt, zinc acrylate, zinc methacrylate or the like is used.

  After adding these zinc halide compounds or unsaturated monocarboxylic acid zinc salts to terminate the polymerization reaction, forming groups derived from zinc halide compounds or unsaturated monocarboxylic acid zinc at the ends of the polymer, methanol, ethanol It is also possible to react with a lower alcohol such as isopropanol or n-butanol to form an alkoxyl group.

  The use of a metal salt of an ethylenically unsaturated carboxylic acid such as zinc salt of acrylic acid or methacrylic acid or magnesium salt as one component of the diene rubber composition is described in Patent Document 4, but here As a rubber composition that improves heat aging resistance and reduces hysteresis loss, (A) a diene rubber, (B) a white filler, (C) a silane coupling agent having an ethylenic double bond, (D As a component of a diene rubber composition comprising a metal salt of an ethylenically unsaturated carboxylic acid, (E) a compound having two or more alkoxysilyl groups in the molecule, and (F) an organic peroxide crosslinking agent It is only used, and the ethylenically unsaturated carboxylic acid metal salt is not involved in the reaction with the diene rubber.

The anionic polymerization used here is a polymerization method that proceeds in the following process.
1) Growth species are generated by the nucleophilic attack of the initiator on the monomer.
2) The growing species further undergoes a nucleophilic attack on the monomer, and the process is repeated to produce a polymer having a growing end.
3) The growing species at the end of the polymer undergoes nucleophilic attack on the terminator and the polymerization stops.
As a result, one start end and one stop end are introduced into each polymer chain. Therefore, ideally, the stopper should be used at a ratio of 1: 1 or 100% with respect to the initiator, but considering that the stopper used this time is ZnX ₂ or divalent, its lower limit The value is about 50 mol%. The amount of the lower alcohol used to form the alkoxyl group is an amount sufficient to completely or partially convert the halogen group or (meth) acryl group to an alkoxyl group.

Next, the present invention will be described with reference to examples.
Example 1
In a two-necked flask with a volume of 100 ml,
Cyclohexane (Kanto Chemicals) 7ml
2,2-ditetrahydrofurylpropane (Tokyo Kasei product) 0.283 g (1.54 mmol)
n-BuLi in 1.64 mol / L n-hexane solution (Kanto Chemicals) 2 ml (3.28 mmol)
Was added at room temperature, and 5.86 g (56.3 mmol) of styrene (Kanto Chemical) was added to the solution.
Was added dropwise at 0 ° C and stirred at room temperature for 3 hours, and then zinc chloride ZnCl ₂ (Kanto Chemical product) 0.756 g (5.55 mmol) was added to the solution.
Was added as a solution of 10 ml of tetrahydrofuran (Kanto Chemical) to terminate the polymerization reaction.

After filtering the reaction mixture with filter paper, the volatile components were distilled off from the filtrate, and a solution in which the residue was dissolved in 30 ml of tetrahydrofuran was dropped into 200 ml of methanol (Kanto Chemicals) to dissolve the soluble components and insoluble components. Separated into ingredients. After repeating the same operation twice, the volatile component was distilled off to obtain 5.39 g (yield 92%) of a white solid as terminal zinc-modified polystyrene. In this case, it is considered that the methanolysis reaction is caused by the methanol used in the purification step (the same applies to Examples 3 and 5 below).
Mn: 3980
Mn (number average molecular weight) is measured by SEC (size exclusion chromatography), and the value is estimated as the molecular weight in terms of polystyrene.
PDI: 1.1
PDI (polydispersity) is calculated as Mw / Mn using the Mw (weight average molecular weight) and Mn values measured by SEC. The closer the PDI value is to 1, the more the polymer whose molecular weight distribution is controlled. Is obtained
R _f : 0.83
The R _f value is measured using TLC (thin layer chromatography) on a silica plate with toluene as the eluent. The smaller the value, the higher the affinity with silica.
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 7.4 to 6.9 (br)
6.9-6.7 (br)
6.7 ~ 6.3 (br)
4.3 ~ 4.2 (br)
3.9 ~ 3.7 (br)
2.5 ~ 2.2 (br)
2.2 ~ 1.7 (br)
1.7-1.3 (br)
1.2 ~ 0.9 (br)
0.8 ~ 0.7 (br)

Example 2
In Example 1, the amount of 2,2-ditetrahydrofurylpropane was changed to 0.257 g (1.39 mmol), the amount of styrene was changed to 5.60 g (53.8 mmol), and zinc acrylate was used instead of zinc chloride in tetrahydrofuran. (Aldrich product) 1.37 g (6.65 mmol) in tetrahydrofuran (10 ml) was used to stop the polymerization reaction by adding 10 ml of methanol, and then the terminal zinc-modified polystyrene white solid 5.32 g (yield 95%) Got.
Mn: 3790
PDI: 1.2
R _f : 0.62
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 7.3 to 6.9 (br)
6.9-6.7 (br)
6.7 ~ 6.3 (br)
6.2〜6.1 (br)
5.9 ~ 5.8 (br)
2.4 ~ 1.7 (br)
1.7-1.3 (br)
1.2 ~ 0.9 (br)
0.8 ~ 0.7 (br)

Example 3
In Example 1, the amount of 2,2-ditetrahydrofurylpropane was changed to 0.291 g (1.58 mmol), the amount of zinc chloride was changed to 0.780 g (5.72 mmol), and 1,3-butadiene was substituted for styrene. Using 17.6 g (48.8 mmol) of a 15 wt% n-hexane solution (product of Aldrich), 2.14 g (yield 81%) of a white viscous liquid as a terminal zinc-modified polybutadiene was obtained.
Mn: 3240
PDI: 1.1
R _f : 0.79
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 5.9 to 5.7 (br)
5.6-5.2 (br)
5.1 ~ 4.8 (br)
4.2 ~ 4.0 (br)
2.3 ~ 1.7 (br)
1.6-1.0 (br)
0.8 ~ 0.7 (br)

Example 4
In Example 3, the amount of 2,2-ditetrahydrofurylpropane was changed to 0.284 g (1.54 mmol), the amount of 1,3-butadiene in a 15 wt% n-hexane solution was changed to 17.2 g (47.7 mmol), and Instead of the solution of zinc chloride in tetrahydrofuran, a solution of 1.36 g (6.60 mmol) of zinc acrylate in tetrahydrofuran (10 ml) was used, and then the polymerization reaction was stopped by adding 10 ml of methanol. 2.04 g (yield 79%) was obtained.
Mn: 2440
PDI: 1.2
R _f : 0.62
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 6.2 to 6.1 (br)
5.9 ~ 5.7 (br)
5.6-5.2 (br)
5.1 ~ 4.9 (br)
3.9 ~ 3.7 (br)
2.3 ~ 1.7 (br)
1.6-1.0 (br)
0.8 ~ 0.7 (br)

Example 5
In Example 1, the amount of 2,2-ditetrahydrofurylpropane was changed to 0.323 g (1.75 mmol), the amount of zinc chloride was changed to 0.791 g (5.80 mmol), and the amount of styrene was changed to 2.90 g (27.8 mmol). Using 15.1 g (41.9 mmol) of a 15 wt% n-hexane solution of 1,3-butadiene as a mixed solution with styrene, 4.34 g (84% yield) of a white viscous liquid that is a terminal zinc-modified poly (styrene-butadiene) Got.
Mn: 4470
PDI: 1.1
R _f : 0.71
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 7.3 to 7.0 (br)
7.0 ~ 6.2 (br)
5.9 ~ 5.8 (br)
5.7-5.0 (br)
5.0 ~ 4.4 (br)
4.2 ~ 4.1 (br)
2.6 ~ 0.9 (br)
0.9-0.7 (br)

Example 6
In Example 5, the amount of 2,2-ditetrahydrofurylpropane was 0.278 g (1.51 mmol), the amount of styrene was 3.09 g (29.7 mmol), and the amount of 15% n-hexane solution of 1,3-butadiene was 17.4 g. The polymerization reaction was stopped by using 1.32 g of zinc acrylate (6.41 mmol) in tetrahydrofuran (10 ml) instead of zinc chloride in tetrahydrofuran, and then adding 10 ml of methanol. As a result, 4.62 g (yield 81%) of a white viscous liquid which is terminal zinc-modified poly (styrene-butadiene) was obtained.
Mn: 4390
PDI: 1.2
R _f : 0.55
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 7.4 to 7.0 (br)
7.0 ~ 6.4 (br)
6.2〜6.1 (br)
5.9 ~ 5.8 (br)
5.8-5.0 (br)
5.0 ~ 4.5 (br)
3.8 ~ 3.6 (br)
2.7 to 0.7 (br)

Comparative Example 1
In a two-necked flask with a volume of 100 ml,
Cyclohexane (Kanto Chemicals) 7ml
2,2-ditetrahydrofurylpropane (Tokyo Kasei product) 0.320 g (1.74 mmol)
n-BuLi in 1.50 mol / L n-hexane solution (Kanto Chemicals) 2 ml (3.00 mmol)
Was added at room temperature, and 5.49 g (52.7 mmol) of styrene (Kanto Chemical) was added to the solution.
Was added dropwise at 0 ° C and stirred at room temperature for 3 hours, and then methanol (Kanto Chemicals) 6 ml was added to the solution.
Was added to stop the polymerization reaction.

After filtering the reaction mixture with filter paper, volatile components were distilled off from the filtrate, and a solution in which the residue was dissolved in 30 ml of tetrahydrofuran (Kanto Chemicals) was dropped into 200 ml of methanol to dissolve the soluble components and insoluble components. Separated into ingredients. The same operation was repeated twice, and then the volatile component was distilled off to obtain 5.16 g (yield 94%) of a white solid as terminal unmodified polystyrene.
Mn: 2820
PDI: 1.1
R _f : 0.90
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 7.4 to 6.9 (br)
6.9-6.2 (br)
2.3 ~ 2.0 (br)
2.0 ~ 1.2 (br)
1.2 ~ 0.9 (br)
0.8 ~ 0.7 (br)

Comparative Example 2
In Comparative Example 1, 2 ml (3.28 mmol) of 1.64 mol / L n-hexane solution of n-BuLi was used instead of the 1.50 mol / L n-hexane solution of n-BuLi, and the amount of styrene was adjusted to 5.81 g (55.8 mmol). The polymerization reaction was stopped by adding 2.26 g (8.67 mmol) of anhydrous SnCl ₄ (Kanto Chemical) instead of methanol, followed by addition of 10 ml of methanol to obtain a white solid 5.52 which is a terminal tin-modified polystyrene. g (95% yield) was obtained.
Mn: 6500
PDI: 1.2
R _f : 0.87
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 7.5 to 6.9 (br)
6.9-6.2 (br)
3.6 ~ 3.3 (br)
2.3 ~ 1.2 (br)
1.2 ~ 0.9 (br)
0.8 ~ 0.7 (br)

Comparative Example 3
In Comparative Example 1, the amount of 2,2-ditetrahydrofurylpropane was changed to 0.267 g (1.45 mmol), the amount of n-BuLi in 1.50 mol / L n-hexane was changed to 1 ml (1.50 mmol), and Instead, the polymerization reaction was stopped by using 16.63 g (46.1 mmol) of a 15 wt% n-hexane solution of 1,3-butadiene, and then adding 8 ml of methanol to obtain 2.22 g of colorless viscous liquid which is a terminal unmodified polybutadiene ( Yield 89%).
Mn: 7820
PDI: 1.1
R _f : 0.82
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 5.8 to 5.7 (br)
5.7-5.2 (br)
5.1 ~ 4.7 (br)
2.5-2.3 (br)
2.2 ~ 1.8 (br)
1.7-0.9 (br)
0.8 ~ 0.7 (br)

Comparative Example 4
In Comparative Example 3, the amount of 2,2-ditetrahydrofurylpropane was changed to 0.296 g (1.61 mmol), and instead of the 1.50 mol / L n-hexane solution of n-BuLi, 1.64 mol / L n- Using 2 ml (3.28 mmol) of hexane solution, the amount of 15% by weight n-hexane solution of 1,3-butadiene was changed to 16.69 g (46.3 mmol), and 3.02 g (11.6 mmol) of anhydrous SnCl _{4 was} added instead of methanol. The polymerization reaction was stopped by addition, and then 10 ml of methanol was added to obtain 2.13 g (yield 85%) of a colorless viscous liquid as terminal tin-modified polybutadiene.
Mn: 5420
PDI: 1.2
R _f : 0.95
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 5.8 to 5.7 (br)
5.7-5.1 (br)
5.1 ~ 4.7 (br)
3.7 ~ 3.2 (br)
2.5 ~ 2.2 (br)
2.2 ~ 1.8 (br)
1.8-0.9 (br)
0.8 ~ 0.7 (br)

Comparative Example 5
In Comparative Example 1, the amount of 2,2-ditetrahydrofurylpropane was changed to 0.331 g (1.80 mmol), and instead of a 1.50 mol / L n-hexane solution of n-BuLi, 1.64 mol / L n- A mixed solution of 1.69 g (25.8 mmol) of styrene and 9.25 g (25.7 mmol) of a 15% by weight n-hexane solution of 1,3-butadiene was used in 1 ml (1.64 mmol) of hexane solution and instead of styrene solution. By adding 8 ml, the polymerization reaction was stopped to obtain 3.51 g (yield 86%) of a white solid which is terminal unmodified poly (styrene-butadiene).
Mn: 9820
PDI: 1.0
R _f : 0.82
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 7.3 to 6.9 (br)
6.9-6.2 (br)
5.9 ~ 4.9 (br)
4.9-4.4 (br)
2.7 to 0.8 (br)
0.8 ~ 0.7 (br)

Comparative Example 6
In Comparative Example 5, the amount of 2,2-ditetrahydrofurylpropane was 0.274 g (1.49 mmol), the amount of n-BuLi in 1.64 mol / L n-hexane was 2 ml (3.28 mmol), and the amount of styrene was 2.54 g ( 24.4 mmol), the amount of 1,3-butadiene in a 15 wt% n-hexane solution was changed to 10.45 g (29.0 mmol), and 1.84 g (7.06 mmol) of anhydrous SnCl ₄ was added in place of methanol. Then, 10 ml of methanol was added to obtain 3.45 g (yield 84%) of a colorless viscous liquid which is a terminal tin-modified polybutadiene.
Mn: 5990
PDI: 1.1
R _f : 0.85
¹ H-NMR (CDCl ₃ , 20 ° C.): δ = 7.4 to 6.9 (br)
6.9-6.2 (br)
5.9 ~ 4.9 (br)
4.9-4.4 (br)
3.7 ~ 3.2 (br)
2.7 to 0.8 (br)
0.8 ~ 0.7 (br)

Claims (8)

  In the presence of an anionic polymerization initiator, a vinyl aromatic monomer, a conjugated diene monomer, or both are polymerized and then a zinc halide compound or an unsaturated monocarboxylic acid zinc salt is added thereto to terminate the polymerization reaction. A method for producing a terminal zinc-modified polymer, characterized by comprising:   After the vinyl aromatic monomer, the conjugated diene monomer or both are polymerized in the presence of an anionic polymerization initiator, the zinc halide compound or unsaturated zinc monocarboxylate is added thereto to stop the polymerization reaction. And a method for producing a terminal zinc-modified polymer, comprising adding a lower alcohol having 1 to 4 carbon atoms.   The method for producing a terminal zinc-modified polymer according to claim 1 or 2, wherein styrene or a derivative thereof is used as the vinyl aromatic monomer.   The method for producing a terminal zinc-modified polymer according to claim 1 or 2, wherein 1,3-butadiene or isoprene is used as the conjugated diene monomer.   The method for producing a terminal zinc-modified polymer according to claim 1 or 2, wherein an organic lithium compound is used as the anionic polymerization initiator.   The method for producing a terminal zinc-modified polymer according to claim 1 or 2, wherein zinc chloride is used as the zinc halide compound.   The method for producing a terminal zinc-modified polymer according to claim 1 or 2, wherein zinc acrylate or zinc methacrylate is used as the unsaturated monocarboxylic acid zinc salt.   The method for producing a terminal zinc-modified polymer according to claim 1 or 2, wherein a polymer having a group derived from a zinc halide compound or an unsaturated zinc monocarboxylate is formed at the terminal site.