Complexed polymer, method for cleaving coordination bond of complexed polymer, and method for reforming coordination bond of complexed polymer

Abstract

The present invention addresses the problem of providing a complexed polymer in which an exchange of crosslinking bonds does not easily occur. The solution to this problem is a complexed polymer comprising at least one polymer chain and a plurality of nitrogen-containing functional groups bonded to the polymer chain and capable of coordination bonding, the coordination-bondable nitrogen-containing functional groups each forming a coordination bond via at least one metal ion selected from the group consisting of iron ions, zinc ions, cobalt ions, and nickel ions, and the complexed polymer being characterized in that the molar ratio of the metal ions to the nitrogen-containing functional groups (metal ions / nitrogen-containing functional groups) is 1 or greater.

Description

Complexed polymer, method for breaking the coordinate bond of a complexed polymer, and method for reforming the coordinate bond of a complexed polymer

[0001] The present invention relates to complexed polymers, methods for breaking the coordination bonds of complexed polymers, and methods for reforming the coordination bonds of complexed polymers.

[0002] Conventionally, most crosslinked rubber products such as used tires have been disposed of without being reused. However, from the viewpoints of environmental issues, resource conservation, etc., recycling of crosslinked rubber waste has become an urgent issue.

[0003] In contrast, Patent Document 1 below discloses, as thermally recyclable crosslinked rubber, a complexed polymer that includes a polymer main chain containing conjugated diene units and / or olefin units and a functional group bonded to the polymer main chain, the functional group containing a nitrogen atom and / or a phosphorus atom and complexed with a metal ion of an element in Groups 7 to 10 of the periodic table, as well as a rubber composition and a rubber product (crosslinked rubber) that include the complexed polymer.The document also discloses that crosslinked rubber containing the complexed polymer can be crushed, remolded, and subjected to heat and pressure to cause crosslink exchange (recombination), and that even the crosslinked rubber can be remolded and reused like a thermoplastic elastomer.

[0004] However, once a thermally recyclable crosslinked rubber such as that described in Patent Document 1 is crosslinked, it cannot be returned to an uncrosslinked state that is free to deform (at room temperature), and therefore the molding process used in normal tire manufacturing cannot be utilized. Therefore, in order to reuse and remanufacture tires as tire materials, it is necessary to return the tires to an uncrosslinked rubber.

[0005] In contrast to this, as a method for returning crosslinked rubber to an uncrosslinked rubber, Patent Document 2 listed below discloses a method for releasing the coordinate bonds of a complexed polymer, which comprises a polymer chain and a plurality of nitrogen- and / or phosphorus-containing functional groups capable of forming coordinate bonds bonded to the polymer chain, wherein the nitrogen- and / or phosphorus-containing functional groups capable of forming coordinate bonds form coordinate bonds with each other via metal ions, and the complexed polymer is dissolved in a solvent containing a free ligand to release the coordinate bonds.

[0006] International Publication No. WO 2022 / 049961 International Publication No. WO 2022 / 049962

[0007] However, crosslinked rubbers that are prone to crosslink exchange (recombination), such as the complex polymer disclosed in the above-mentioned Patent Document 1, are easy to recycle by heat, but are prone to deformation due to strain such as compression or extension (i.e., poor creep resistance and permanent set resistance), and cannot be used in durable products that are subjected to strain for a long period of time, such as tires and hoses. In order to ensure these performances, there is a demand for complex polymers that are less prone to crosslink exchange (recombination), such as sulfur-crosslinked rubbers.

[0008] On the other hand, in order to improve properties such as creep resistance and permanent set resistance, a method of increasing the crosslink density has been considered. However, the higher the crosslink density, the more the molecular flow is hindered even when heat is applied (i.e., the material becomes harder and less likely to deform), and the crosslinked molecular chains are less likely to intertwine (because they are less likely to mix), making molding more difficult. Furthermore, the crosslink density is likely to vary between the surface and the interior of the crushed crosslinked rubber, and the properties of the recycled crosslinked rubber, such as fracture resistance and durability, are significantly reduced compared to before recycling. Thus, the performance of crosslinked rubber and its thermal recyclability are in a trade-off relationship.

[0009] Furthermore, in the method described in the above-mentioned Patent Document 2, the solvent and free ligands coordinate to the metal ions instead of the functional groups of the complexed polymer, thereby making it possible to achieve an (apparently) decrosslinked state in the solvent. However, the inventors' investigations revealed that, when the solvent and free ligands are removed, the functional groups bonded to the polymer chains return to a crosslinked state in which they form coordinate bonds via the metal ions, making it difficult to stably obtain a decrosslinked rubber.

[0010] Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a complexed polymer that is less susceptible to crosslink exchange (recombination). Another object of the present invention is to provide a method for breaking the coordinate bonds of a complexed polymer, which makes it possible to stably obtain a decrosslinked rubber, and a method for reforming the coordinate bonds of such a complexed polymer.

[0011] The complexed polymer, the method for breaking the coordinate bond of the complexed polymer, and the method for reforming the coordinate bond of the complexed polymer of the present invention, which solve the above problems, are outlined as follows.

[0012] [1] A complex polymer having at least one polymer chain and a plurality of nitrogen-containing functional groups capable of forming coordinate bonds bonded to the polymer chain, wherein the nitrogen-containing functional groups capable of forming coordinate bonds form coordinate bonds with each other via at least one metal ion selected from the group consisting of iron ions, zinc ions, cobalt ions, and nickel ions, wherein the molar ratio of the metal ions to the nitrogen-containing functional groups (metal ions / nitrogen-containing functional groups) is 1 or more.

[0013] [2] The complex polymer according to [1], wherein the nitrogen-containing functional group is derived from a compound having a triazine ring or a tetrazine ring, and a pyridyl group or a pyrimidinyl group is bonded to the triazine ring or the tetrazine ring.

[0014] [3] The nitrogen-containing functional group is represented by the following general formula (1): [In the formula, X １ and X ２ are each independently a pyridyl group or a pyrimidinyl group, and Y １ and Y ２ are each independently a single bond or a divalent hydrocarbon group.

[0015] [4] X in the above general formula (1) １ and X ２ is a pyridyl group, and Y １ and Y ２ is a single bond.

[0016] [5] The complex polymer according to any one of [1] to [4], wherein the metal ion is an iron ion.

[0017] [6] A method for breaking the coordinate bond of a complexed polymer, comprising a step of breaking the coordinate bond of the complexed polymer according to any one of [1] to [5] with an alkali metal hydroxide.

[0018] [7] The method for releasing the coordinate bond of a complex polymer according to [6], wherein the alkali metal hydroxide is at least one selected from the group consisting of potassium hydroxide and sodium hydroxide.

[0019] [8] A method for reforming a coordinate bond of a complexed polymer, comprising: a step of dissociating the coordinate bond of the complexed polymer according to any one of [1] to [5] with an alkali metal hydroxide; and a step of reforming the coordinate bond of the complexed polymer whose coordinate bond has been dissolved with at least one metal ion selected from the group consisting of iron ions, zinc ions, cobalt ions, and nickel ions.

[0020] [9] The method for reforming a coordinate bond of a complex polymer according to [8], wherein the metal ion in the step of reforming the coordinate bond is an iron ion.

[0021]

[10] The method for reforming a coordinate bond of a complexed polymer according to [8] or [9], wherein the coordinate bond of the complexed polymer, the coordinate bond of which has been released, is reformed by the metal ion in the presence of a sulfenamide compound.

[0022]

[11] The method for reforming the coordinate bond of a complex polymer according to

[10] , wherein the sulfenamide compound is at least one selected from the group consisting of N-cyclohexylbenzothiazole-2-sulfenamide and N-(tert-butyl)benzothiazole-2-sulfenamide.

[0023] According to the present invention, it is possible to provide a complexed polymer that is less susceptible to crosslink exchange (recombination), and also to provide a method for breaking the coordinate bonds of a complexed polymer, which makes it possible to stably obtain a decrosslinked rubber, and a method for reforming the coordinate bonds of such a complexed polymer.

[0024] 1 shows a GPC chart of the decrosslinked rubber (functionalized polymer) obtained after decrosslinking in Example 4, and a GPC chart of functionalized polymer D.

[0025] The complex polymer of the present invention, the method for breaking the coordinate bond of the complex polymer, and the method for reforming the coordinate bond of the complex polymer will be described in detail below with reference to the embodiments.

[0026] <Definitions> The compounds described herein may be derived in part or in whole from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0027] <Complexed Polymer> The complexed polymer of this embodiment has at least one polymer chain and a plurality of nitrogen-containing functional groups capable of forming coordinate bonds attached to the polymer chain. Furthermore, in the complexed polymer of this embodiment, the nitrogen-containing functional groups capable of forming coordinate bonds form coordinate bonds with each other via at least one metal ion selected from the group consisting of iron ions, zinc ions, cobalt ions, and nickel ions. The complexed polymer of this embodiment is characterized in that the molar ratio of the metal ions to the nitrogen-containing functional groups (metal ions / nitrogen-containing functional groups) is 1 or greater.

[0028] In the complex polymer of the present embodiment, polymer chains having nitrogen-containing functional groups form coordinate bonds via metal ions, and the molar ratio of the metal ions to the nitrogen-containing functional groups (metal ions / nitrogen-containing functional groups) is 1 or more, which makes crosslink exchange (recombination) less likely to occur, and the complex polymer exhibits performance similar to that of a sulfur-crosslinked rubber.

[0029] (Polymer Chain) The complexed polymer of this embodiment has at least one polymer chain. When there is one polymer chain, the complexed polymer forms a coordinate bond via a metal ion within the molecule, resulting in crosslinking. When there are two or more polymer chains, coordinate bonds can be formed via metal ions not only within the molecule but also between molecules (between polymer chains), resulting in crosslinking. The complexed polymer of this embodiment has a plurality of nitrogen-containing functional groups capable of forming coordinate bonds, and the plurality of nitrogen-containing functional groups may be bonded to one polymer chain or may be bonded separately to two or more polymer chains. The plurality of nitrogen-containing functional groups may be the same or different.

[0030] The polymer chain preferably contains conjugated diene units and / or olefin units, i.e., the polymer chain preferably contains conjugated diene units or olefin units, or both conjugated diene units and olefin units.

[0031] The conjugated diene unit is a monomer unit derived from a conjugated diene compound. The conjugated diene compound used as a monomer preferably has 4 to 8 carbon atoms. Specific examples of such conjugated diene compounds include 1,3-butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. From the viewpoint of good elastomeric properties, the conjugated diene compound used as a monomer preferably contains 1,3-butadiene and / or isoprene. The proportion of the conjugated diene unit in the polymer chain is not particularly limited and may be 0 mol %, but is preferably 0.1 mol % or more, more preferably 1 mol % or more, and may even be 100 mol %. When the proportion is 1 mol % or more, a complexed polymer with excellent elastomeric properties is obtained.

[0032] The olefin unit is a monomer unit derived from an olefin compound. The olefin compound as a monomer preferably has 2 to 10 carbon atoms. Specific examples of such olefin compounds include α-olefins such as ethylene, propylene, 1-pentene, 1-hexene, 1-heptene, and 1-octene, and heteroatom-substituted alkene compounds such as vinyl pivalate, 1-phenylthioethene, and N-vinylpyrrolidone. The proportion of the olefin unit in the polymer chain is not particularly limited and may be 0 mol %, but is preferably 1 mol % or more, and may also be 100 mol %.

[0033] The polymer chain may contain units derived from other monomers copolymerizable with the conjugated diene compound and / or the olefin compound. Examples of such units derived from other monomers include aromatic vinyl units. The proportion of units derived from other monomers in the polymer chain is not particularly limited and may be 0 mol %, but in one embodiment, it is preferably 1 mol % or more and 50 mol % or less. The aromatic vinyl units are monomer units derived from aromatic vinyl compounds. The aromatic vinyl compounds refer to aromatic compounds substituted with at least a vinyl group. The aromatic vinyl compounds used as monomers preferably have 8 to 10 carbon atoms. Specific examples of such aromatic vinyl compounds include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2-ethylstyrene, 3-ethylstyrene, and 4-ethylstyrene.

[0034] (Nitrogen-Containing Functional Group) The complex polymer of this embodiment has a plurality of nitrogen-containing functional groups capable of forming coordinate bonds attached to the polymer chain. The nitrogen-containing functional groups capable of forming coordinate bonds form coordinate bonds with each other via metal ions. Because of the coordinate bonds, sufficient reversibility can be imparted to the bond between the metal ion and the nitrogen-containing functional group. Furthermore, the coordinate bond between the nitrogen-containing functional group and the metal ion is sufficiently strong, and can form a crosslink with a strength equivalent to that of sulfur crosslinking, so the complex polymer of this embodiment has sufficient durability. As the nitrogen-containing functional group, a group containing a nitrogen-containing heterocycle such as a 4,5-dihydropyridazine ring, a pyridine ring, a pyrimidine ring, a triazine ring, or a tetrazine ring is preferred.

[0035] Here, the nitrogen-containing functional group preferably does not contain a sulfur atom, which can suppress crosslinking between polymer chains due to sulfur atoms, thereby improving the recyclability of the complex polymer.

[0036] In the complex polymer, the bond dissociation energy between the metal ion and the nitrogen-containing functional group is preferably 200 kJ / mol or more, more preferably 250 kJ / mol or more, and preferably 500 kJ / mol or less. A bond dissociation energy of 200 kJ / mol or more allows a stronger crosslinked structure to be formed, further improving the durability of the complex polymer. A bond dissociation energy of 250 kJ / mol or more further improves the durability of the complex polymer. A bond dissociation energy of 500 kJ / mol or less allows the coordinate bond between the metal ion and the nitrogen-containing functional group to be more easily dissolved, making the complex polymer more easily recyclable.

[0037] In the present invention, the bond dissociation energy between a metal ion and a nitrogen-containing functional group is a value calculated at the M06 / 6-31G(d,p) / / B3PW91-D3 / 6-31G(d,p) level or the M06 / 6-31G(d,p) level in a vacuum. It is considered that the metal ion and the nitrogen-containing functional group form ionic aggregates. Gaussian 09 or GRRM14 can be used to calculate the bond dissociation energy.

[0038] The nitrogen-containing functional group is preferably derived from a compound having a triazine ring or a tetrazine ring. Compounds containing a triazine ring or a tetrazine ring have high reactivity with polymer chains and easily form functionalized polymers by reacting with the polymer chains. Furthermore, the nitrogen-containing functional group derived from a compound containing a triazine ring or a tetrazine ring is easily complexed with metal ions to form crosslinks, thereby forming a crosslinked structure with higher strength.

[0039] Here, it is preferable that a pyridyl group or a pyrimidinyl group be bonded to the triazine ring or the tetrazine ring of the compound having a triazine ring or a tetrazine ring, and it is even more preferable that two pyridyl groups or two pyrimidinyl groups be bonded to the triazine ring or the tetrazine ring. When the nitrogen-containing functional group is derived from a compound having a triazine ring or a tetrazine ring and a pyridyl group or a pyrimidinyl group is bonded to the triazine ring or the tetrazine ring, the nitrogen-containing functional group and the metal ion are more easily complexed, the bond dissociation energy is more easily increased, and a crosslinked structure with even higher strength can be formed. Furthermore, when two pyridyl groups or two pyrimidinyl groups are bonded to the triazine ring or the tetrazine ring, the nitrogen-containing functional group and the metal ion are more easily complexed, the bond dissociation energy is more easily increased, and a crosslinked structure with even higher strength can be formed. The pyridyl group may be a 2-pyridyl group, a 3-pyridyl group, or a 4-pyridyl group, but a 2-pyridyl group is preferred. The pyrimidinyl group may be a 2-pyrimidinyl group, a 4-pyrimidinyl group, or a 5-pyrimidinyl group.

[0040] The nitrogen-containing functional group is represented by the following general formula (1): [In the formula, X １ and X ２ are each independently a pyridyl group or a pyrimidinyl group, and Y １ and Y ２ are each independently a single bond or a divalent hydrocarbon group. The compound represented by general formula (1) is preferably derived from a compound represented by the formula:

[0023] . The compound represented by general formula (1) is likely to undergo a Diels-Alder reaction with a polymer chain and easily form a functionalized polymer. Furthermore, when the nitrogen-containing functional group is derived from a compound represented by general formula (1), the nitrogen-containing functional group and metal ions are particularly likely to complex, and the bond dissociation energy is particularly likely to be high, allowing the formation of a crosslinked structure with even greater strength.

[0041] In the above general formula (1), X １ and X ２ are each independently a pyridyl group or a pyrimidinyl group. １ and X ２is preferably a pyridyl group. The pyridyl group may be a 2-pyridyl group, a 3-pyridyl group, or a 4-pyridyl group, with a 2-pyridyl group being preferred. The pyrimidinyl group may be a 2-pyrimidinyl group, a 4-pyrimidinyl group, or a 5-pyrimidinyl group.

[0042] In the above general formula (1), Y １ and Y ２ are each independently a single bond or a divalent hydrocarbon group. Here, examples of the divalent hydrocarbon group include an alkylene group, an alkenylene group, and an arylene group. More specifically, examples of the alkylene group include a methylene group, an ethylene group, a trimethylene group, and a tetramethylene group. Examples of the alkenylene group include a vinylene group, a propenylene group, and a butenylene group. Examples of the arylene group include a phenylene group, a tolylene group, and a naphthylene group. From the viewpoint of ease of synthesis, Y １ and Y ２ is preferably a single bond (i.e., X is not attached to the tetrazine ring). １ and X ２ is preferably directly bonded).

[0043] Here, X in the general formula (1) １ and X ２ is a pyridyl group, and Y １ and Y ２ is preferably a single bond. In this case, the compound of formula (1) is easily available, and is particularly likely to form a complex with a metal ion, and the bond dissociation energy is particularly likely to be high, making it possible to form a crosslinked structure with even higher strength.

[0044] The compounds represented by the general formula (1) include 3,6-di(2-pyridyl)-1,2,4,5-tetrazine, 3,6-di(3-pyridyl)-1,2,4,5-tetrazine, 3,6-di(4-pyridyl)-1,2,4,5-tetrazine, 3,6-di(2-pyridylmethyl)-1,2,4,5-tetrazine, 3,6-di(2-pyridylethyl)-1,2,4,5-tetrazine, 3-(2-pyridyl)-1,2,4,5-tetrazine, lysylmethyl)-6-(2-pyridylethyl)-1,2,4,5-tetrazine, 3,6-di(2-pyrimidinyl)-1,2,4,5-tetrazine, 3,6-di(4-pyrimidinyl)-1,2,4,5-tetrazine, 3,6-di(5-pyrimidinyl)-1,2,4,5-tetrazine, and the like. Among these, 3,6-di(2-pyridyl)-1,2,4,5-tetrazine is preferred.

[0045] In the complex polymer of this embodiment, the nitrogen-containing functional group is preferably bonded in an amount of 0.1 to 10 mol % relative to the monomer units in the polymer chain, more preferably 0.3 to 8 mol %, even more preferably 0.4 to 5 mol %, and particularly preferably 0.5 to 3 mol %. When the nitrogen-containing functional group is bonded in an amount of 0.1 mol % or more relative to the monomer units in the polymer chain, crosslinks with a strength equivalent to that of sulfur crosslinks can be formed, resulting in a complex polymer with sufficient durability. Furthermore, when the nitrogen-containing functional group is bonded in an amount of 10 mol % or less relative to the monomer units in the polymer chain, a complex polymer with sufficient elastomeric properties is likely to be obtained.

[0046] The complex polymer of the present embodiment may further have another functional group that does not form a coordinate bond with a metal ion. Such another functional group is not particularly limited and can be appropriately selected depending on the physical properties of the target complex polymer.

[0047] (Metal Ion) In the complex polymer of this embodiment, the nitrogen-containing functional groups capable of forming a coordinate bond form a coordinate bond with each other via at least one metal ion selected from the group consisting of iron ions, zinc ions, cobalt ions, and nickel ions. Iron ions, zinc ions, cobalt ions, and nickel ions tend to form stronger coordinate bonds with the nitrogen-containing functional groups, allowing for the formation of a stronger crosslinked structure. Note that the valence of the metal ions is not particularly limited, and each element can have any valence.

[0048] As the metal ion, an iron ion is particularly preferable. The iron ion is likely to bond particularly strongly with the nitrogen-containing functional group, and can form a crosslinked structure with even greater strength. The valence of the iron ion is divalent (Fe ２＋ ) or trivalent (Fe ３＋ ) is preferred.

[0049] In the complex polymer of this embodiment, the molar ratio of the metal ion to the nitrogen-containing functional group (metal ion / nitrogen-containing functional group) is 1 or more. When the molar ratio of the metal ion to the nitrogen-containing functional group (metal ion / nitrogen-containing functional group) is 1 or more, cross-link exchange (recombination) is less likely to occur, and the complex polymer exhibits performance similar to that of a sulfur-crosslinked rubber. Note that, from the viewpoint of further reducing the likelihood of cross-link exchange (recombination), the complex polymer of this embodiment preferably has a molar ratio (metal ion / nitrogen-containing functional group) of 1.1 or more, and since increasing the molar ratio beyond a certain level reduces the effect (causes saturation), the molar ratio (metal ion / nitrogen-containing functional group) is preferably 2.0 or less.

[0050] For example, by adding a metal salt to a polymer chain to which the nitrogen-containing functional group is bonded, the metal ion can form a coordinate bond with the nitrogen-containing functional group of the polymer chain. In this case, a complex polymer can be easily obtained and a crosslinked structure with high strength can be formed. The form of the metal salt to be added is not particularly limited, and may be, for example, a hydrate. The amount of metal salt (metal ion) added can be appropriately selected so that the molar ratio of the metal ion to the nitrogen-containing functional group (metal ion / nitrogen-containing functional group) is 1 or more.

[0051] Examples of the metal salt include metal halides, metal sulfates, and metal nitrates, and among these, metal halides are preferred. Metal halides are easy to handle and can form a crosslinked structure with high strength.

[0052] Examples of the metal halide include metal fluorides, metal chlorides, metal bromides, and metal iodides, and among these, metal chlorides are preferred. Metal chlorides are easier to handle and can form a crosslinked structure with high strength.

[0053] Specific examples of the metal salt include FeCl ２ , FeCl ２ ・4H ２ O, FeCl ３ , FeCl ３ ・6H ２ O. The metal salt may be a single type or a combination of two or more types.

[0054] (Method for Producing Complex Polymer) The complex polymer of this embodiment can be synthesized, for example, by reacting a compound having a nitrogen-containing functional group with a polymer chain to form a functionalized polymer in which the nitrogen-containing functional group is bonded to the polymer chain, and then complexing the functionalized polymer with a metal ion. Here, the compound having the nitrogen-containing functional group is preferably a compound having a triazine ring or a tetrazine ring as described above, and more preferably a compound represented by general formula (1). Furthermore, in the reaction between the polymer chain and the compound having the nitrogen-containing functional group, the reaction conditions such as temperature, pressure, and time are preferably selected appropriately depending on the type and reactivity of the polymer chain and the compound having the nitrogen-containing functional group used. Furthermore, in the complexation reaction between the functionalized polymer and the metal ion, the reaction conditions such as temperature, pressure, and time are preferably selected appropriately depending on the type and reactivity of the functionalized polymer and the metal ion used.

[0055] As an example, 3,6-di(2-pyridyl)-1,2,4,5-tetrazine is used as a compound having a nitrogen-containing functional group, and iron chloride (FeCl) is used as a source of metal ions. ２The reaction scheme for functionalization of the polymer chain and complexation of the functionalized polymer using .

[0056] As shown in the upper part of the reaction scheme above, a functionalized polymer can be produced by the Diels-Alder reaction of a polymer chain having an unsaturated bond with a compound having a nitrogen-containing functional group. In this example, nitrogen is eliminated during the Diels-Alder reaction, but any other reaction may be used for the functionalization reaction.

[0057] As shown in the lower part of the above reaction scheme, the functionalized polymer and iron chloride are complexed and crosslinked to form a complexed polymer. While the above reaction scheme shows a coordinate bond between the nitrogen atom in the tetrazine residue, the nitrogen atom of the pyridyl group bonded to the tetrazine residue, and the iron ion (complexation and crosslinking), the complexed polymer can take various complexation forms.

[0058] In the above reaction scheme, one nitrogen-containing functional group derived from 3,6-di(2-pyridyl)-1,2,4,5-tetrazine is coordinated to two iron ions, and one iron ion is coordinately bonded to parts of the two nitrogen-containing functional groups, so that the two nitrogen-containing functional groups and the two iron ions form a crosslinked structure through coordinate bonds. When the molar ratio of the metal ion to the nitrogen-containing functional group (metal ion / nitrogen-containing functional group) is 1 or greater, most of the nitrogen-containing functional group is coordinated to the metal ion, as shown in the lower part of the above reaction scheme, making crosslink exchange (recombination) less likely to occur.

[0059] The complexing polymer of the present embodiment may be prepared in advance by synthesis or the like as described above, but may also be generated in situ during the production process of the rubber composition, for example.

[0060] For example, in the first stage of kneading in the production process of the rubber composition, a polymer chain and a compound having a nitrogen-containing functional group are kneaded together to form a functionalized polymer in which the nitrogen-containing functional group is bonded to the polymer chain, and in the second or subsequent stages of kneading, a metal salt is added and kneaded to complex the functionalized polymer to form a complex polymer. In this case, the production of the rubber composition and the synthesis of the complex polymer can be carried out simultaneously.

[0061] Alternatively, for example, a functionalized polymer having a nitrogen-containing functional group bonded to a polymer chain may be prepared in advance, and the functionalized polymer may be kneaded with any compounding ingredients in the first stage of kneading in the production process of the rubber composition. In the second or subsequent stage of kneading, a metal salt may be added and kneaded to complex the functionalized polymer to form a complex polymer. In this case, the production of the rubber composition and the synthesis of the complex polymer can be carried out simultaneously.

[0062] <Method for Dissolving Coordination Bonds of Complexed Polymer> The method for dissolving coordination bonds of a complexed polymer of this embodiment is characterized by including the step of dissolving the coordination bonds of the complexed polymer of this embodiment using an alkali metal hydroxide.

[0063] In the method for breaking the coordination bond of a complexed polymer of this embodiment, a technique for breaking the coordination bond of a complexed polymer (crosslinked rubber) is used, in which an alkali metal hydroxide is applied to convert the metal ion into a hydroxide or oxide, thereby deactivating the nitrogen coordination ability of the metal ion. Furthermore, by deactivating the nitrogen coordination ability of the metal ion, the coordination bond (metal coordination bond) of the complexed polymer can be easily broken (broken), and the crosslinking between polymer chains can be more easily eliminated, allowing a functionalized polymer to be obtained as an uncrosslinked rubber. Furthermore, according to the method for breaking the coordination bond of a complexed polymer of this embodiment, since the nitrogen coordination ability of the metal ion is deactivated, a decrosslinked rubber can be stably obtained.

[0064] The alkali metal hydroxide is preferably at least one selected from the group consisting of potassium hydroxide and sodium hydroxide. Potassium hydroxide and sodium hydroxide are excellent in converting metal ions into hydroxides or oxides, and are capable of easily deactivating the nitrogen-coordinating ability of metal ions, more easily breaking the coordinate bonds of the complexed polymer, and more easily eliminating crosslinks between polymer chains.

[0065] The amount of the alkali metal hydroxide used is not particularly limited, but is preferably in the range of 2 to 50 mol, more preferably 5 to 20 mol, per mol of metal ions in the complex polymer. If the amount of alkali metal hydroxide used is within this range, the metal ions are more likely to be converted into hydroxides or oxides, and the nitrogen-coordinating ability of the metal ions is more likely to be deactivated.

[0066] The alkali metal hydroxide may be added to the complexing polymer as a solution, or the complexing polymer may be added to a solution of the alkali metal hydroxide. Examples of solvents used to prepare the solution include alcohols such as methanol and ethanol, and ethers such as tetrahydrofuran (THF). The concentration of the alkali metal hydroxide in the solution is preferably in the range of 0.01 to 5 mol / L, and more preferably in the range of 0.1 to 3 mol / L.

[0067] <Method for reforming coordinate bonds of complexed polymer> The method for reforming coordinate bonds of a complexed polymer of the present embodiment is characterized by comprising the steps of: dissociating the coordinate bonds of the complexed polymer of the present embodiment using an alkali metal hydroxide; and reforming the coordinate bonds of the complexed polymer (i.e., functionalized polymer) whose coordinate bonds have been dissolved using at least one metal ion selected from the group consisting of iron ions, zinc ions, cobalt ions, and nickel ions.

[0068] In the method for reforming the coordinate bond of a complexed polymer of this embodiment, the coordinate bond of the complexed polymer (i.e., the functionalized polymer (uncrosslinked rubber) obtained by decrosslinking the complexed polymer) whose coordinate bond has been released, which is obtained by the above-mentioned method for releasing the coordinate bond of a complexed polymer of this embodiment, can be reformed using metal ions, thereby returning the complexed polymer (crosslinked rubber) to the original state (recycled).

[0069] (Step of Dissolving Coordination Bonds of Complexed Polymer) In the method of reforming the coordination bonds of a complexed polymer of this embodiment, the step of dissolving the coordination bonds of the complexed polymer with an alkali metal hydroxide is the same as the method of dissolving the coordination bonds of a complexed polymer of this embodiment described above, and preferred embodiments, preferred materials, etc. are also the same.

[0070] (Step of reforming the coordinate bond of the complexed polymer) The method of reforming the coordinate bond of the complexed polymer of this embodiment includes a step of reforming the coordinate bond of the complexed polymer that has been released using at least one metal ion selected from the group consisting of iron ions, zinc ions, cobalt ions, and nickel ions. Here, the metal ions used to reform the coordinate bond may be the same type as or different from the metal ions used to produce the complexed polymer. Suitable aspects and suitable materials for the metal ions used to reform the coordinate bond are the same as those for the metal ions of the complexed polymer of this embodiment described above.

[0071] As the metal ion in the step of reforming the coordinate bond, an iron ion is particularly preferable. The iron ion is likely to form a particularly strong bond with the nitrogen-containing functional group, and can reform a crosslinked structure with even greater strength. The valence of the iron ion is divalent (Fe ２＋ ) or trivalent (Fe ３＋ ) is preferred.

[0072] In the reformation of the coordinate bond, the molar ratio of the metal ion to the nitrogen-containing functional group (metal ion / nitrogen-containing functional group) is preferably 1 or more. When the molar ratio of the metal ion to the nitrogen-containing functional group (metal ion / nitrogen-containing functional group) is 1 or more, cross-link exchange (recombination) is less likely to occur even after the reformation of the coordinate bond, and the complexed polymer obtained by reforming the coordinate bond exhibits performance similar to that of a sulfur-crosslinked rubber. From the viewpoint of further reducing the likelihood of cross-link exchange (recombination), the molar ratio (metal ion / nitrogen-containing functional group) is more preferably 1.1 or more. Furthermore, since increasing the molar ratio beyond a certain level reduces the effect (causes saturation), the molar ratio (metal ion / nitrogen-containing functional group) is preferably 2.0 or less.

[0073] In one embodiment, the coordination bond can be reformed by adding a new metal ion (e.g., a metal salt) to the complexed polymer (i.e., functionalized polymer) whose coordination bond has been released and heating the polymer. When a metal salt is added as the metal ion, suitable examples of the metal salt to be added are the same as those mentioned in the above section on "complexed polymer."

[0074] In the method for reforming the coordinate bond of the complexed polymer of this embodiment, it is preferable to reform the coordinate bond of the complexed polymer that has been released using the metal ion in the presence of a sulfenamide compound. The sulfenamide compound has the effect of promoting the formation of a coordinate bond (metal coordinate bond), and reforming the coordinate bond in the presence of the sulfenamide compound allows the crosslinked structure to be reformed in a shorter time.

[0075] The sulfenamide compound is a compound having a sulfenamide structure in the molecule, and examples of the sulfenamide compound include N-cyclohexylbenzothiazole-2-sulfenamide, N-(tert-butyl)benzothiazole-2-sulfenamide, N,N-dicyclohexylbenzothiazole-2-sulfenamide, N-oxydiethylenebenzothiazole-2-sulfenamide, N-methylbenzothiazole-2-sulfenamide, N-ethylbenzothiazole-2-sulfenamide, N-propylbenzothiazole-2-sulfenamide, N-butylbenzothiazole-2-sulfenamide, N-pentylbenzothiazole-2-sulfenamide, N-hexylbenzothiazole-2-sulfenamide, N-heptylbenzothiazole-2-sulfenamide, N-octylbenzothiazole-2-sulfenamide, N-(2-ethylhexyl)benzothiazole-2-sulfenamide, N-decylbenzothiazole-2-sulfenamide, N-dodecyl ... benzothiazole-2-sulfenamide, N-stearylbenzothiazole-2-sulfenamide, N,N-dimethylbenzothiazole-2-sulfenamide, N,N-diethylbenzothiazole-2-sulfenamide, N,N-dipropylbenzothiazole-2-sulfenamide, N,N-dibutylbenzothiazole-2-sulfenamide, N,N-dipentylbenzothiazole-2-sulfenamide, N,N-dihexylbenzothiazole-2-sulfenamide, N,N-diheptyl Examples of suitable benzothiazole-2-sulfenamide include benzothiazole-2-sulfenamide, N,N-dioctylbenzothiazole-2-sulfenamide, N,N-di(2-ethylhexyl)benzothiazole-2-sulfenamide, N,N-didodecylbenzothiazole-2-sulfenamide, and N,N-distearylbenzothiazole-2-sulfenamide. Of these, N-cyclohexylbenzothiazole-2-sulfenamide and N-(tert-butyl)benzothiazole-2-sulfenamide are preferred.When the sulfenamide compound is at least one selected from the group consisting of N-cyclohexylbenzothiazole-2-sulfenamide and N-(tert-butyl)benzothiazole-2-sulfenamide, the crosslinked structure can be reformed in a shorter time.

[0076] The amount of the sulfenamide compound used is not particularly limited, but is preferably in the range of 0.1 to 1.0 mol, and more preferably in the range of 0.2 to 0.5 mol, per mol of metal ion used to reform the coordinate bond (crosslinked structure). When the amount of the sulfenamide compound used is within this range, the crosslinked structure can be reformed in an even shorter time.

[0077] (Applications) The complexed polymer of this embodiment and the complexed polymer obtained by the method of this embodiment for reforming the coordinate bond of the complexed polymer can be applied to various rubber products and resin products. Examples of such rubber products include tires, rubber vibration absorbers, rubber seismic isolation devices, conveyor belts, rubber crawlers, and various hoses. By applying the method of this embodiment for breaking the coordinate bond of the complexed polymer to these rubber products, the coordinate bond of the complexed polymer in the rubber product can be broken, and the functionalized polymer can be recovered, allowing the complexed polymer to be recycled.

[0078] When the complexed polymer is applied to a rubber product, it is preferable to prepare a rubber composition containing the complexed polymer and use the rubber composition in at least a portion of the rubber product by, for example, molding the rubber composition into a desired shape. The rubber composition contains the complexed polymer as a rubber component, and may further contain a rubber component other than the complexed polymer. Examples of such other rubber components include natural rubber (NR), synthetic diene rubber, and non-diene rubber. Examples of synthetic diene rubbers include synthetic isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene rubber (SIR), chloroprene rubber (CR), ethylene-butadiene copolymer, and ethylene-styrene-butadiene copolymer. Examples of non-diene rubbers include silicone rubber, fluororubber, and urethane rubber. The rubber component of the rubber composition preferably contains the complexed polymer in a proportion of 10% by mass or more, and the proportion of the complexed polymer may be 100% by mass.

[0079] In addition to the rubber component containing the complexing polymer described above, the rubber composition may contain compounding agents commonly used in the rubber industry, such as fillers (carbon black, silica, etc.), softeners, stearic acid, antioxidants, silane coupling agents, etc., which are appropriately selected and compounded. Commercially available products can be suitably used as these compounding agents. The rubber composition preferably contains a small amount of sulfur or peroxide, or does not contain any sulfur. Even when the rubber composition contains a small amount of sulfur or does not contain any sulfur, the rubber composition may contain a vulcanization accelerator, and preferably contains a vulcanization accelerator. The vulcanization accelerator preferably contains a sulfenamide-based vulcanization accelerator.

[0080] The complexed polymer may be produced during the production process of the rubber composition. For example, in the first stage of kneading, a polymer chain and a compound containing a functional group are kneaded to form a functionalized polymer in which the functional group is bonded to the polymer chain, and in the second stage or later of kneading, a metal salt is added and kneaded to complex the functionalized polymer to form a complexed polymer. In this case, the complexed polymer can be prepared during the production of the rubber composition (kneading of the rubber composition), resulting in excellent productivity. Note that the complexation of the functionalized polymer by adding a metal salt can be carried out at any stage from the second stage onwards of kneading. Furthermore, in the first stage, second stage or later of kneading, any compounding agent as described above may be simultaneously blended. Furthermore, as the compound containing a functional group, the above-mentioned compound containing a triazine ring or tetrazine ring is preferred, and a compound represented by general formula (1) is more preferred.

[0081] Further, for example, the complex polymer may be formed in advance and then blended during kneading to produce a rubber composition. Such a method for producing a rubber composition also makes it possible to easily produce a rubber composition containing the complex polymer, and also has excellent productivity.

[0082] Alternatively, for example, a functionalized polymer having a functional group bonded to a polymer chain may be prepared in advance, and the functionalized polymer may be kneaded with any compounding ingredients in a first stage of kneading. In a second or subsequent stage of kneading, a metal salt may be added and kneaded to complex the functionalized polymer to form a complex polymer. This method of producing a rubber composition also makes it possible to easily produce a rubber composition containing the complex polymer, and is also excellent in productivity.

[0083] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0084] <Method for producing functionalized polymers A, B, and C> Using a conventional laboratory mixer, styrene-butadiene rubber (SBR), 3,6-di(2-pyridyl)-1,2,4,5-tetrazine (manufactured by Tokyo Chemical Industry Co., Ltd.), and carbon black (HAF grade) were added to the formulations shown in Table 1, and the mixture was kneaded at 140°C for 3 minutes to prepare functionalized polymers A, B, and C (mixtures of functionalized polymer and carbon black).

[0085] <Method for Producing Unfunctionalized Polymer> Using a conventional laboratory mixer according to the formulation shown in Table 1, 50 parts by mass of carbon black (HAF grade) was added to 100 parts by mass of styrene-butadiene rubber (SBR), and the mixture was kneaded at 140°C for 3 minutes to prepare an unfunctionalized polymer (a mixture of an unfunctionalized polymer and carbon black).

[0086]

[0087] *1 SBR: Styrene-butadiene rubber, manufactured by Asahi Kasei Corporation, product name "Tufden 2000R"

[0088] Example 1 Using a conventional laboratory mixer, iron (II) chloride tetrahydrate and antioxidant (6C) were added to functionalized polymer A according to the formulation shown in Table 2, and the mixture was kneaded at 60°C for 1 minute, and then pressed in a mold at 160°C for 60 minutes to prepare a complex polymer.

[0089] <Permanent Set Evaluation Test> The obtained complex polymer was subjected to a compression set test at a temperature of 70°C and a compression ratio of 20% in accordance with JIS K6262, and the calculated compression set (%) is shown in Table 2. Furthermore, the obtained complex polymer was subjected to an elongation tensile set test at a temperature of 70°C and an elongation ratio of 100% in accordance with JIS K6273, and the calculated tensile set (%) is shown in Table 2.

[0090] <Evaluation of Thermal Recyclability> The obtained complexed polymer was cut into pieces of approximately 2 to 3 mm on a side to prepare granular rubber, which was then laid out in a 2 mm thick slab sheet mold and pressed at 160°C for 60 minutes to evaluate the thermal recyclability of the complexed polymer. The evaluation criteria are as follows: Poor: When the granular rubber remains Good: When the granular rubber can be bonded and integrated together, but there are irregularities on the sheet surface Excellent: When the rubber can be remolded well and the surface is smooth The results are shown in Table 2.

[0091] (Examples 2 and 3) Complex polymers were prepared according to the formulations shown in Table 2 in the same manner as in Example 1. The resulting complex polymers were subjected to a compression set test, an elongation tensile set test, and an evaluation of thermal recyclability in the same manner as in Example 1. The results are shown in Table 2.

[0092] Comparative Example 1 A sulfur-crosslinked rubber was prepared by adding zinc oxide, an antioxidant, a vulcanization accelerator, and sulfur to an unfunctionalized polymer according to the formulation shown in Table 2, kneading the mixture at 80°C for 1 minute, and then pressing the mixture in a mold at 160°C for 20 minutes. The resulting sulfur-crosslinked rubber was subjected to a compression set test, an elongation tensile set test, and an evaluation of thermal recyclability in the same manner as in Example 1. The results are shown in Table 2.

[0093] Comparative Example 2 A complex polymer was prepared using the formulation shown in Table 2 (the molar ratio of iron to nitrogen-containing functional group was less than 1) in the same manner as in Example 1. The resulting complex polymer was subjected to a compression set test, an elongation tensile set test, and an evaluation of thermal recyclability in the same manner as in Example 1. The results are shown in Table 2.

[0094]

[0095] *2 Antioxidant 6C: N-(1,3-dimethylbutyl)-N'-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Co., Ltd., trade name "Knocklac 6C" *3 Vulcanization accelerator DM: Dibenzothiazyl disulfide, manufactured by Ouchi Shinko Chemical Co., Ltd., trade name "Noccela DM-P" *4 Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazolyl sulfenamide, manufactured by Ouchi Shinko Chemical Co., Ltd., trade name "Noccela CZ-G"

[0096] Table 2 shows that the complex polymers of Examples, in which the molar ratio of metal ions to nitrogen-containing functional groups (metal ions / nitrogen-containing functional groups) is 1 or more, have good thermal recyclability and small permanent set. On the other hand, the complex polymer of Comparative Example 2, in which the molar ratio of metal ions to nitrogen-containing functional groups (metal ions / nitrogen-containing functional groups) is less than 1, has large permanent set and poor durability.

[0097] [Evaluation of recyclability via chemical decrosslinking] <Preparation of functionalized polymer D> Using a conventional laboratory mixer, styrene-butadiene rubber (SBR) and 3,6-di(2-pyridyl)-1,2,4,5-tetrazine (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to the compounding formulation shown in Table 3, and the mixture was kneaded at 160°C for 3 minutes to prepare functionalized polymer D.

[0098] <Preparation of Complexed Polymer D> Next, iron (II) chloride tetrahydrate was added to Functionalized Polymer D, and the mixture was kneaded at 60°C for 1 minute, and then pressed in a mold at 160°C for 120 minutes to prepare Complexed Polymer D.

[0099]

[0100] *1 SBR: Styrene-butadiene rubber, manufactured by Asahi Kasei Corporation, product name "Tufden 2000R"

[0101] Example 4 Complexed polymer D was cut into pieces approximately 2-3 mm on a side to prepare rubber granules, which were then immersed in a mixed solution of the concentration shown in Table 4 at 65°C for 5 hours to undergo a decrosslinking reaction. In Example 4, KOH (decrosslinking agent) was dissolved in methanol in advance to prepare a 1 mol / L methanol solution, and the rubber granules were dissolved in tetrahydrofuran (THF) to prepare a THF solution. The KOH methanol solution and the rubber granule THF solution were mixed in a volume ratio of 10:90 to prepare a mixed solution. The amount of mixed solution used was 20 mL per 1 g of rubber granules (crosslinked rubber). The solution in which the granular rubber had been decrosslinked and became uniform was added to a large amount of methanol to precipitate a rubber component, and the resulting precipitated rubber was redissolved in the same amount of THF solvent as the amount used in the mixed solution, and again added to a large amount of methanol to precipitate a rubber component. The alkali metal in the rubber component was removed, and then the rubber component was dried under reduced pressure to obtain a decrosslinked rubber (functionalized polymer).

[0102] <Measurement of storage modulus G'> The obtained decrosslinked rubber was heated at 160°C for 1 minute (until the value of storage modulus G' stabilized) using a rubber processability analyzer (RPA2000 manufactured by Alpha Technologies), and the storage modulus G' was measured. The results are shown in Table 5.

[0103] <Evaluation of THF solubility> The solubility of the obtained decrosslinked rubber in THF was evaluated. Good: Soluble Insoluble: Insoluble The results are shown in Table 5.

[0104] <Weight-average molecular weight measurement> A chart based on the polystyrene (PS)-equivalent molecular weight of the decrosslinked rubber (functionalized polymer) was obtained by gel permeation chromatography ("HLC-8320" manufactured by Tosoh Corporation, two "TSKgel GMHXL" columns connected in series, column temperature: 40°C, eluent: tetrahydrofuran, detector: differential refractometer (RI)), and the weight-average molecular weight (Mw) was determined based on the chart. The chart of the decrosslinked rubber (functionalized polymer) obtained in Example 4 and the chart of functionalized polymer D for comparison are shown in Figure 1, and the weight-average molecular weight (Mw) is shown in Table 5.

[0105] <Evaluation of Re-crosslinking of Decrosslinked Rubber> Using a conventional laboratory mixer, iron (II) chloride tetrahydrate and a vulcanization accelerator were added to the decrosslinked rubber (functionalized polymer) according to the formulation shown in Table 5, and the mixture was kneaded at 100°C for 5 minutes, followed by pressing in a mold at 160°C for 60 minutes to re-crosslink, thereby preparing a complexed polymer. The complexed polymer obtained was subjected to a tensile test at room temperature in accordance with JIS K 6301-1995, and the modulus of elasticity at 200% elongation (Md200%) of the re-crosslinked rubber was measured. The index, where Md200% of complexed polymer D is taken as 100, is shown in Table 5. A larger index value indicates a higher network density and the formation of crosslinked bonds.

[0106] (Examples 5 to 7) In the same manner as in Example 4, a decrosslinking reaction was carried out under the conditions shown in Table 4. The storage modulus G' and THF solubility of the obtained decrosslinked rubber were evaluated in the same manner as in Example 4. The results are shown in Table 5. Furthermore, for Examples 5 and 7, recrosslinking evaluation was carried out using the compounding formulation shown in Table 5 in the same manner as in Example 4. The results are shown in Table 5.

[0107] (Comparative Example 3) Complexed polymer D was cut into pieces approximately 2 to 3 mm on a side to prepare granular rubber, which was then immersed in a mixed solution of pyridine and THF in the mixing ratio shown in Table 4 at 65°C for 12 hours to carry out a decrosslinking reaction. After the granular rubber was decrosslinked and became homogeneous, the solution was added to a large amount of methanol to precipitate the rubber component, which was then dried under reduced pressure to obtain precipitated rubber. The solubility of the obtained rubber in THF was evaluated. Good: Soluble Poor: Insoluble The results are shown in Table 5. The result was that the rubber was insoluble in THF, which is thought to be due to it having returned to its original crosslinked state.

[0108]

[0109]

[0110] *4 Vulcanization accelerator CZ: N-cyclohexylbenzothiazole-2-sulfenamide, manufactured by Ouchi Shinko Chemical Co., Ltd., trade name "Noccela CZ-G"

[0111] Tables 4 and 5 show that the alkali metal hydroxide can break the coordinate bonds of the complexed polymer and effectively remove the crosslinks.

[0112] Table 5 also shows that the decrosslinked rubber (functionalized polymer) obtained by decrosslinking can be recrosslinked with metal ions and has good physical properties. Furthermore, a comparison of Examples 4 and 5 with Example 7 shows that by recrosslinking the decrosslinked rubber (functionalized polymer) obtained by decrosslinking in the presence of a sulfenamide compound, it is possible to restore excellent physical properties equal to or greater than those of the original complexed polymer.

[0113] The complexed polymer of the present invention can be used in various rubber products such as tires, etc. Furthermore, the method of the present invention for breaking the coordinate bond of the complexed polymer and the method of reforming the coordinate bond of the complexed polymer can be used for recycling the polymer.

Claims

1. A complex polymer having at least one polymer chain and a plurality of nitrogen-containing functional groups capable of forming coordinate bonds attached to the polymer chain, wherein the nitrogen-containing functional groups capable of forming coordinate bonds form coordinate bonds with each other via at least one metal ion selected from the group consisting of iron ions, zinc ions, cobalt ions, and nickel ions, wherein the molar ratio of the metal ions to the nitrogen-containing functional groups (metal ions / nitrogen-containing functional groups) is 1 or greater.

2. The complex polymer according to claim 1, wherein the nitrogen-containing functional group is derived from a compound having a triazine ring or a tetrazine ring, and a pyridyl group or a pyrimidinyl group is bonded to the triazine ring or the tetrazine ring.

3. The nitrogen-containing functional group is represented by the following general formula (1): [In the formula, X １ and X ２ are each independently a pyridyl group or a pyrimidinyl group, and Y １ and Y ２ and each independently represents a single bond or a divalent hydrocarbon group.

4. X in the above general formula (1) １ and X ２ is a pyridyl group, and Y １ and Y ２ The complexing polymer of claim 3 , wherein is a single bond.

5. The complexing polymer of claim 1, wherein the metal ion is an iron ion.

6. A method for releasing the coordinate bond of a complex polymer, comprising the step of releasing the coordinate bond of the complex polymer according to any one of claims 1 to 5 with an alkali metal hydroxide.

7. The method for releasing the coordinate bond of a complexed polymer according to claim 6, wherein the alkali metal hydroxide is at least one selected from the group consisting of potassium hydroxide and sodium hydroxide.

8. A method for reforming the coordinate bond of a complexed polymer, comprising the steps of: breaking the coordinate bond of the complexed polymer according to any one of claims 1 to 5 with an alkali metal hydroxide; and reforming the coordinate bond of the complexed polymer whose coordinate bond has been broken with at least one metal ion selected from the group consisting of iron ions, zinc ions, cobalt ions, and nickel ions.

9. The method for reforming coordinate bonds of a complexed polymer according to claim 8, wherein the metal ion in the step of reforming coordinate bonds is an iron ion.

10. A method for reforming the coordinate bond of a complexed polymer according to claim 8, which comprises reforming the coordinate bond of the complexed polymer that has been released with the metal ion in the presence of a sulfenamide compound.

11. The method for reforming the coordinate bond of a complexed polymer according to claim 10, wherein the sulfenamide compound is at least one selected from the group consisting of N-cyclohexylbenzothiazole-2-sulfenamide and N-(tert-butyl)benzothiazole-2-sulfenamide.

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