US-12617927-B2 - Method for cleaving coordinate bond of complex polymer

Abstract

A method for cleaving a coordinate bond of a complex polymer that contains at least one polymer chain and a plurality of nitrogen- and/or phosphorus-containing functional groups which are bonded to the polymer chain and capable of forming coordinate bonds, wherein the coordinately-bondable nitrogen- and/or phosphorus-containing functional groups form a coordinate bond via a metal ion, characterized in that the method includes dissolving the complex polymer in a solvent containing a free ligand, to cleave the coordinate bond.

Inventors

• Tomoyuki KOSAI

Assignees

• BRIDGESTONE CORPORATION

Dates

Publication Date

20260505

Application Date

20210802

Priority Date

20200904

Claims (20)

1. 1 . A method for cleaving a coordinate bond of a complex polymer that contains at least two polymer chains and a plurality of nitrogen- and/or phosphorus-containing functional groups which are bonded to the polymer chains and capable of forming coordinate bonds, the complex polymer containing a conjugated diene unit and/or an olefin unit, wherein the coordinately-bondable nitrogen- and/or phosphorus-containing functional groups form coordinate bonds via a metal ion intramolecularly and intermolecularly, thereby forming a crosslink between the polymer chains, so that the complex polymer constitutes a rubber, characterized in that the method comprises: dissolving the complex polymer in a solvent containing a free ligand, to cleave the coordinate bond of the complex polymer by a ligand exchange reaction between the free ligand and the complex polymer, thereby either completely or partially dissociating the metal ion from the plurality of nitrogen- and/or phosphorus-containing functional groups and breaking down the crosslink between the polymer chains of the rubber, and wherein the method involves no hydrolysis.
2. 2 . The method for cleaving a coordinate bond of a complex polymer according to claim 1 , wherein the plurality of nitrogen- and/or phosphorus-containing functional groups contain no sulfur atom.
3. 3 . The method for cleaving a coordinate bond of a complex polymer according to claim 1 , wherein plurality of the nitrogen- and/or phosphorus-containing functional groups are derived from a compound containing a triazine ring or a tetrazine ring.
4. 4 . The method for cleaving a coordinate bond of a complex polymer according to claim 3 , wherein a pyridyl group or a pyrimidinyl group is bonded to the triazine ring or the tetrazine ring.
5. 5 . The method for cleaving a coordinate bond of a complex polymer according to claim 4 , wherein two pyridyl groups or pyrimidinyl groups are bonded to the triazine ring or the tetrazine ring.
6. 6 . The method for cleaving a coordinate bond of a complex polymer according to claim 3 , wherein the plurality of nitrogen- and/or phosphorus-containing functional groups are derived from a compound represented by general formula (1) shown below: in the general formula (1), each of X 1 and X 2 independently represents a pyridyl/pyrimidinyl group, and each of Y 1 and Y 2 independently represents a single bond or a divalent hydrocarbon group.
7. 7 . The method for cleaving a coordinate bond of a complex polymer according to claim 6 , wherein each of X 1 and X 2 is a pyridyl group and each of Y 1 and Y 2 is a single bond in the general formula (1).
8. 8 . The method for cleaving a coordinate bond of a complex polymer according to claim 1 , wherein the metal ion is selected from metal ions of elements of Groups 7 to 10 in the Periodic Table.
9. 9 . The method for cleaving a coordinate bond of a complex polymer according to claim 8 , wherein the metal ion is a metal ion of an element of Group 8 in the Periodic Table.
10. 10 . The method for cleaving a coordinate bond of a complex polymer according to claim 9 , wherein the metal ion is an iron ion.
11. 11 . The method for cleaving a coordinate bond of a complex polymer according to claim 1 , wherein the plurality of nitrogen- and/or phosphorus-containing functional groups are bonded to the polymer chains by an amount of the functional groups in the range of 0.1 mol % to 10 mol % with respect to a monomer unit in the polymer chains.
12. 12 . The method for cleaving a coordinate bond of a complex polymer according to claim 1 , wherein a bond dissociation energy for dissociation of the metal ion and the plurality of nitrogen- and/or phosphorus-containing functional groups is 200 kJ/mol or more.
13. 13 . The method for cleaving a coordinate bond of a complex polymer according to claim 1 , wherein the free ligand is a compound containing nitrogen and/or phosphorus.
14. 14 . The method for cleaving a coordinate bond of a complex polymer according to claim 13 , wherein the compound containing nitrogen and/or phosphorus is a nitrogen-containing aromatic compound.
15. 15 . The method for cleaving a coordinate bond of a complex polymer according to claim 14 , wherein the nitrogen-containing aromatic compound is selected from pyridine and pyrimidine.
16. 16 . The method for cleaving a coordinate bond of a complex polymer according to claim 13 , wherein the compound containing nitrogen and/or phosphorus is an amine compound.
17. 17 . The method for cleaving a coordinate bond of a complex polymer according to claim 1 , wherein the solvent is an organic solvent.
18. 18 . The method for cleaving a coordinate bond of a complex polymer according to claim 17 , wherein the organic solvent is selected from tetrahydrofuran, hexane, and cyclohexane.
19. 19 . The method for cleaving a coordinate bond of a complex polymer according to claim 1 , wherein the solvent is exclusively a non-aqueous organic solvent.
20. 20 . The method for cleaving a coordinate bond of a complex polymer according to claim 1 , wherein the free ligand is selected from pyridine and pyrimidine.

Description

TECHNICAL FIELD The present invention relates to a method for cleaving a coordinate bond of a complex polymer. BACKGROUND Conventionally, most of vulcanized rubber products which have been used, such as used tires, were disposed as waste without being recycled. However, now it is an urgent task to recycle such waste of vulcanized rubber as used tires in terms of addressing environmental problems, facilitating resource-saving, and so on. As a method for regenerating a vulcanized rubber, there is, for example, a conventionally known method for regenerating a vulcanized rubber by applying heat and shearing force to the vulcanized rubber by using a twin-screw extruder. Further, PTL 1 proposes a technique of devulcanizing a vulcanized rubber and regenerating the rubber as an unvulcanized rubber. CITATION LIST Patent Literature PTL 1: JP2005-023225 A SUMMARY OF THE INVENTION Technical Problem However, in the prior art, a crosslinked product of polymer, such as a vulcanized rubber, inevitably deteriorates as a result of regeneration because the crosslinked product is regenerated by being treated under harsh conditions. A rubber product using a regenerated rubber has, for example, a problem that the rubber product performs poorly in physical properties such as breaking strength, as compared with a rubber product not using a regenerated rubber. Accordingly, there is still room for improvement in recycling a crosslinked product of polymer, such as a vulcanized rubber, whereby a further study thereon is being requested. In view of this, an object of the present disclosure is to solve the prior art problem described above and provide a method capable of easily breaking down a crosslink of a polymer (such as rubber). Solution to Problem As a result of a keen study for solving the problems described above, the inventor of the present disclosure discovered that, for a specific complex polymer forming a coordinate bond via a metal ion, the crosslink therein can be easily broken down by dissolving the complex polymer in a solvent containing a free ligand. The present disclosure has been completed on the basis of the discovery. Specifically, the primary features of the present disclosure for achieving the aforementioned objects are as follows. A method for cleaving a coordinate bond of a complex polymer according to the present disclosure is a method for cleaving a coordinate bond of a complex polymer that contains at least one polymer chain and a plurality of nitrogen- and/or phosphorus-containing functional groups which are bonded to the polymer chain and capable of forming coordinate bonds, wherein the coordinately-bondable nitrogen- and/or phosphorus-containing functional groups form coordinate bonds via a metal ion, characterized in that the method including dissolving the complex polymer in a solvent containing a free ligand, to cleave the coordinate bond. Advantageous Effect According to the present disclosure, it is possible to provide a method capable of easily breaking down a crosslink of a polymer. DETAILED DESCRIPTION Hereinafter, a method for cleaving a coordinate bond of a complex polymer according to the present disclosure will be demonstratively described in detail by way of embodiments thereof. <Method for Cleaving Coordinate Bond of Complex Polymer> A method for cleaving a coordinate bond of a complex polymer according to the present disclosure is a method for cleaving a coordinate bond of a complex polymer that contains at least one polymer chain and a plurality of nitrogen- and/or phosphorus-containing functional groups which are bonded to the polymer chain and capable of forming coordinate bonds, wherein the coordinately-bondable nitrogen- and/or phosphorus-containing functional groups form coordinate bonds via a metal ion, characterized in that the method including dissolving the complex polymer in a solvent containing a free ligand, to cleave the coordinate bond. The complex polymer subjected to the method according to the present disclosure has at least one polymer chain and a plurality of nitrogen- and/or phosphorus-containing functional groups bonded to the polymer chain and capable of forming coordinate bonds, wherein the coordinately bondable nitrogen- and/or phosphorus-containing functional groups form coordinate bonds via a metal ion therebetween. The complex polymer has a crosslinking structure due to the nitrogen- and/or phosphorus-containing functional groups forming coordinate bonds via metal ion therebetween. When the complex polymer is dissolved in a solvent containing a free ligand, a ligand exchange reaction takes place and the free ligand forms a coordinate bond with the metal ion, whereby the coordinate bond of the complex polymer (more specifically, the coordinate bond between the metal ion and the nitrogen- and/or phosphorus-containing functional groups bonded to the polymer chain) can be easily cleaved and thus the crosslink between the polymer chains can be easily broken down. Acco